Wilhelm Brünings' forgotten contribution to the metabolic treatment of cancer utilizing hypoglycemia and a very low carbohydrate (ketogenic) diet

Ketogenic diet does not promote triple-negative and luminal mammary tumor growth and metastasis in experimental mice

Ketogenic diets (KDs) can improve the well-being and quality of life of breast cancer patients. However, data on the effects of KDs on mammary tumors are inconclusive, and the influence of KDs on metastasis in general remains to be investigated. We therefore assessed the impact of a KD on growth and metastasis of triple negative murine 4T1 mammary tumors, and on the progression of luminal breast tumors in an autochthonous MMTV-PyMT mouse model. We found that KD did not influence the metastasis of 4T1 and MMTV-PyMT mammary tumors, but impaired 4T1 tumor cell proliferation in vivo, and also temporarily reduced 4T1 primary tumor growth. Notably, the ketogenic ratio (the mass of dietary fat in relation to the mass of dietary carbohydrates and protein) that is needed to induce robust ketosis was twice as high in mice as compared to humans. Surprisingly, only female but not male mice responded to KD with a sustained increase in blood β-hydroxybutyrate levels. Together, our data show that ketosis does not foster primary tumor growth and metastasis, suggesting that KDs can be safely applied in the context of luminal breast cancer, and may even be advantageous for patients with triple negative tumors. Furthermore, our data indicate that when performing experiments with KDs in mice, the ketogenic ratio needed to induce ketosis must be verified, and the sex of the mice should also be taken into account.

Dietary approaches for exploiting metabolic vulnerabilities in cancer

Renewed interest in tumor metabolism sparked an enthusiasm for dietary interventions to prevent and treat cancer. Changes in diet impact circulating nutrient levels in the plasma and the tumor microenvironment, and preclinical studies suggest that dietary approaches, including caloric and nutrient restrictions, can modulate tumor initiation, progression, and metastasis. Cancers are heterogeneous in their metabolic dependencies and preferred energy sources and can be addicted to glucose, fructose, amino acids, or lipids for survival and growth. This dependence is influenced by tumor type, anatomical location, tissue of origin, aberrant signaling, and the microenvironment. This review summarizes nutrient dependencies and the related signaling pathway activations that provide targets for nutritional interventions. We examine popular dietary approaches used as adjuvants to anticancer therapies, encompassing caloric restrictions, including time-restricted feeding, intermittent fasting, fasting-mimicking diets (FMDs), and nutrient restrictions, notably the ketogenic diet. Despite promising results, much of the knowledge on dietary restrictions comes from in vitro and animal studies, which may not accurately reflect real-life situations. Further research is needed to determine the optimal duration, timing, safety, and efficacy of dietary restrictions for different cancers and treatments. In addition, well-designed human trials are necessary to establish the link between specific metabolic vulnerabilities and targeted dietary interventions. However, low patient compliance in clinical trials remains a significant challenge.

Anti-tumor effects of ketogenic diets and their synergism with other treatments in mice: Bayesian evidence synthesis of 1755 individual mouse survival data

BACKGROUND

Ketogenic diets (KDs) are high-fat diets with putative anti-tumor effects. The aim of this study was to synthesize the evidence for the anti-tumor effects of KDs in mice, with a focus on their possible synergism with chemotherapy (CT), radiotherapy (RT), or targeted therapies (TT).

METHODS

Relevant studies were retrieved from a literature search. A total of 43 articles reporting on 65 mouse experiments fulfilled the inclusion criteria, and 1755 individual mouse survival times were collated from the study authors or the publications. The restricted mean survival time ratio (RMSTR) between the KD and control groups served as the effect size. Bayesian evidence synthesis models were used to estimate pooled effect sizes and to assess the impact of putative confounders and synergism between KD and other therapies.

RESULTS

Overall, there was a significant survival-prolonging effect of KD monotherapy (RMSTR = 1.161 ± 0.040), which was confirmed in meta-regression accounting for syngeneic versus xenogeneic models, early versus late KD start and subcutaneous versus other organ growth. Combining the KD with RT or TT, but not CT, was associated with a further 30% (RT) or 21% (TT) prolongation of survival. An analysis accounting for 15 individual tumor entities showed that KDs exerted significant survival-prolonging effects in pancreatic cancer (all treatment combinations), gliomas (KD + RT and KD + TT), head and neck cancer (KD + RT), and stomach cancer (KD+RT and KD + TT).

CONCLUSIONS

This analytical study confirmed the overall anti-tumor effects of KDs in a large number of mouse experiments and provides evidence for synergistic effects with RT and TT.

Cancer Metabolism: Fasting Reset, the Keto-Paradox and Drugs for Undoing

In tumor cells, ketolysis "via" succinyl-CoA: 3-oxoacid-CoAtransferase (SCOT) and acetyl-CoA acetyltransferase 1 (ACAT1) is a major source of mitochondrial acetyl-CoA. Active ACAT1 tetramers stabilize by tyrosine phosphorylation, which facilitates the SCOT reaction and ketolysis. Tyrosine phosphorylation of pyruvate kinase PK M2 has the opposite effect, stabilizing inactive dimers, while pyruvate dehydrogenase (PDH), which is already inhibited by phosphorylation, is acetylated by ACAT1 and is doubly locked. This closes the glycolytic supply of acetyl-CoA. In addition, since tumor cells must synthesize fatty acids to create new membranes, they automatically turn off the degradation of fatty acids into acetyl-CoA ("via" the malonyl-CoA brake for the fatty acid carnityl transporter). Thus, inhibiting SCOT the specific ketolytic enzyme and ACAT1 should hold back tumor progression. However, tumor cells are still able to take up external acetate and convert it into acetyl-CoA in their cytosol "via" an acetyl-CoA synthetase, which feeds the lipogenic pathway; additionally, inhibiting this enzyme would make it difficult for tumor cells to form new lipid membrane and survive.

Cancer—A Pragmatic Switch to Combat Metabolic Syndrome?

Both cancer and metabolic disease have become the prevalent health risks in modern societies worldwide. Cancer is a complex set of illnesses with many definitions. About 15% of cancers are caused by infections, and 10% carry a hereditary burden. The remaining 70%–75% cancers are associated with a variety of processes, often associated with metabolic syndrome and chronic inflammation. This review examines the role of metabolic dysfunction and chronic inflammation in cancer development. I propose a novel concept of a switch, in which our intelligent body uses its sophisticated set of subsystems and sensors to pragmatically anticipate and combat metabolic dysfunction as its’ most direct and dire threat first, while temporarily accepting cancer as a state that in any other circumstances would be considered detrimental, and utilizing cancer as an additional tool to lower glucose levels. Once metabolic dysfunction has been resolved this switch is reversed, and cancer growth will be impaired.

Thiazolidine-2,4-dione derivative exhibits antitumoral effect and reverts behavioral and metabolic changes in a model of glioblastoma

The aim of the present study was to evaluate the anti-glioma activity of 3-(4-fluorobenzyl)-5-(4-methoxybenzylidene)thiazolidine-2,4-dione (AV23) in a preclinical model of glioblastoma, as well as behavioral parameters and toxicological profile. The implantation of C6 cells in the left striatum of male Wistar rats was performed by stereotaxic surgery. After recovery, animals were treated with vehicle (canola oil) or AV23 (10 mg/kg/day) intragastrically for 15 days. It was found that AV23 reduced tumor volume by 90%. Serum biochemical parameters such as triglycerides, cholesterol, HDL-cholesterol, LDL-cholesterol, albumin, aspartate aminotransferase, urea, creatinine and total proteins were not changed; however, there was a slight increase in alanine aminotransferase. The compound AV23 reverted the hypoglycemia and the reduction in body weight caused by glioblastoma. Additionally, AV23 was able to revert the reduction of locomotion caused by the tumor implantation. Therefore, the compound AV23 can be considered a promising candidate in the treatment of glioblastoma.

In vitro gastrointestinal digestion and fermentation models and their applications in food carbohydrates

Food nutrients plays a crucial role in human health, especially in gastrointestinal (GI) health. The effect of food nutrients on human health mainly depends on the digestion and fermentation process in the GI tract. In vitro GI digestion and fermentation models had the advantages of reproducibility, simplicity, universality, and could integrally simulate the in vivo conditions to mimic oral, gastric, small intestinal and large intestinal digestive processes. They could not only predict the relationship among material composition, structure and digestive characteristics, but also evaluate the bioavailability of material components and the impact of digestive metabolites on GI health. This review systematicly summarized the current state of the in vitro simulation models, and made detailed descriptions for their applications, advantages and disadvantages, and specially their applications in food carbohydrates. In addition, it also provided the suggestions for the improvement of in vitro models and firstly proposed to establish a set of standardized methods of in vitro dynamic digestion and fermentation conditions for food carbohydrates, which were in order to further evaluate more effects of the nutrients on human health in future.

Effectiveness of Ketogenic Diets on the Survival of Adult Oncological Patients

Cancer is the second most prevalent disease worldwide and it presents characteristic hallmarks common to all its types. Within these, it has been described a reprogramming of its energy metabolism, characterized by the preferential use of glucose as energy source in an aerobic glycolysis process. Although this feature may provide adaptive advantages to tumoral cells, it has been described as a weakness that could make them more vulnerable. The ketogenic diet, characterized by high fat and very low carbohydrate intake, aims to eliminate glucose, the main fuel used by cancer cells. Animal studies have described promising results in terms of survival and regression of tumor size; nonetheless, these have failed to replicate in human studies. Furthermore, the ketogenic diet presents possible adverse effects when used in the long term, which should be considered in a vulnerable population such as cancer patients. To date, there is no solid evidence to demonstrate the effectiveness of the ketogenic diet in tumor progression or in overall survival of cancer patients, since most of the studies are observational, uncontrolled, and of short duration. At the moment, we only have limited data to guide us, and at the same time, to promote further study of this approach as a therapeutic opportunity.

Cuprizone-Induced Demyelination in Mouse Hippocampus Is Alleviated by Ketogenic Diet

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). Recently, ketogenic diet (KD) supplementation has attracted great interest. Therefore, we established the cuprizone (CPZ)-induced demyelination mouse model to investigate the possible neuroprotective effect of KD on the hippocampus of mice. We found that KD significantly elevated the level of serum β-hydroxybutyric acid, improved behavioral and motor abnormalities, and impaired the spatial learning and memory of CPZ-induced demyelination mice. Meanwhile, KD lessened the hippocampal demyelination by enhancing the expression of mature oligodendrocytes (OLs), which was revealed by the elevated expression of MBP and CNPase, as well as the luxol fast blue-staining intensity. Furthermore, KD inhibits the activation of microglia (especially M1-like microglia) and reactive astrocytes. Interestingly, KD attenuated the CPZ-induced oxidative stress by decreasing the malondialdehyde (MDA) content and restoring the glutathione (GSH) levels. In addition, the double immunofluorescence staining revealed that KD enhanced the expression of SIRT1 in astrocytes, microglia, and mature oligodendrocytes. Concomitantly, Western blot demonstrated that KD increased the expression of SIRT1, phosphorylated-AKT, mTOR, and PPAR-γ. In conclusion, KD exerted a neuroprotective effect on CPZ-induced demyelination mice, and this activity was associated with the modulation of the SIRT1/PPAR-γ and SIRT1/P-Akt/mTOR pathways.

Ketogenic diets in medical oncology: a systematic review with focus on clinical outcomes

Preclinical data provide evidence for synergism between ketogenic diets (KDs) and other oncological therapies. The aim of this systematic review was to summarize data from clinical studies that have tested KDs along with other treatments used within medical oncology. The PubMed database was searched using the key words "ketogenic" AND ("cancer" OR "glioblastoma"). A secondary search was conducted by screening the reference lists of relevant articles on this topic. Relevant studies for this review were defined as studies in which KDs were used complementary to surgery, radio-, chemo-, or targeted therapy and at least one of the following four outcomes were reported: (i) Overall survival (OS); (ii) progression-free survival (PFS); (iii) local control rate; (iv) body composition changes. Twelve papers reporting on 13 clinical studies were identified. Nine studies were prospective and six had a control group, but only two were randomized. KD prescription varied widely between studies and was described only rudimentarily in most papers. Adverse events attributed to the diet were rare and only minor (grade 1-2) except for one possibly diet-related grade 4 event. Studies reporting body composition changes found beneficial effects of KDs in both overweight and frail patient populations. Beneficial effects of KDs on OS and/or PFS were found in four studies including one randomized controlled trial. Studies in high-grade glioma patients were not sufficiently powered to prove efficacy. Evidence for beneficial effects of KDs during cancer therapy is accumulating, but more high-quality studies are needed to assess the overall strength of evidence.

Revisiting the Warburg Effect: Diet-Based Strategies for Cancer Prevention

It is widely acknowledged that cancer cell energy metabolism relies mainly on anaerobic glycolysis; this phenomenon is described as the Warburg effect. However, whether the Warburg effect is caused by genetic dysregulation in cancer or is the cause of cancer remains unknown. The exact reasons and physiology of this abnormal metabolism are unclear; therefore, many researchers have attempted to reduce malignant cell growth in tumors in preclinical and clinical studies. Anticancer strategies based on the Warburg effect have involved the use of drug compounds and dietary changes. We recently reviewed applications of the Warburg effect to understand the benefits of this unusual cancer-related metabolism. In the current article, we summarize diet strategies for cancer treatment based on the Warburg effect.

A ketogenic diet exerts beneficial effects on body composition of cancer patients during radiotherapy: An interim analysis of the KETOCOMP study

Background and aim

Ketogenic diets (KDs) have gained interest as a complementary treatment for cancer patients. Here we present first results of our ongoing KETOCOMP study (NCT02516501) concerning body composition changes among rectal, breast and head & neck cancer (HNC) patients who consumed a KD during curative radiotherapy (RT).

Experimental procedure

Sixty-one patients eating a non-ketogenic diet were compared to 20 patients on a KD supplemented with 10 g essential amino acids on RT days. Body composition was measured prior to and weekly during RT using 8-electrode bioimpedance analysis. Longitudinal body composition data were analyzed using linear mixed effects models.

Results and conclusion

Patients on the KD exhibited nutritional ketosis, defined as serum β-hydroxybutyrate levels ≥0.5 mmol/l, in a median of 69.0% of blood measurements (range 0–100%) performed in our clinic. In rectal and breast cancer patients, KD was significantly associated with a loss of 0.5 and 0.4 kg fat mass per week (p = 0.00089 and 8.49 × 10⁻⁵, respectively), with no significant changes in fat free and skeletal muscle mass. In HNC patients, concurrent chemotherapy was the strongest predictor of body weight, fat free and skeletal muscle mass loss during RT, while consuming a KD was significantly associated with a gain in these measures. These preliminary results confirm prior reports indicating that KDs are safe to consume during standard-of-care therapy. They also provide an important first indication that KDs with ample amino acid intake could improve body composition during RT in curative cancer patients.

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Consumption of a ketogenic diet (KD) during radio(chemo-)therapy is feasible.

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In rectal and breast cancer patients, the KD significantly reduced fat mass.

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Fat-free mass and skeletal muscle mass were preserved by the KD.

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In head and neck cancer patients a KD influenced body composition opposite to chemotherapy.