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Data from the American Cancer Society show that the rate of increase in cancer deaths/year (3.4%) was two-fold greater than the rate of increase in new cases/year (1.7%) from 2013 to 2017

cancer is predicted to overtake heart disease as the leading cause of death in Western societies

cancer can also be recognized as a metabolic disease.

glucose is first split into two molecules of pyruvate through the Embden–Meyerhof–Parnas glycolytic pathway in the cytosol

Aerobic fermentation, on the other hand, involves the production of lactic acid under normoxic conditions

persistent lactic acid production in the presence of adequate oxygen is indicative of abnormal respiration

Otto Warburg first proposed that all cancers arise from damage to cellular respiration

The Crabtree effect is an artifact of the in vitro environment and involves the glucose-induced suppression of respiration with a corresponding elevation of lactic acid production even under hyperoxic (pO2 = 120–160 mmHg) conditions associated with cell culture

the Warburg theory of insufficient aerobic respiration remains as the most credible explanation for the origin of tumor cells [2, 37, 51, 52, 53, 54, 55, 56, 57].

The main points of Warburg’s theory are; 1) insufficient respiration is the predisposing initiator of tumorigenesis and ultimately cancer, 2) energy through glycolysis gradually compensates for insufficient energy through respiration, 3) cancer cells continue to produce lactic acid in the presence of oxygen, and 4) respiratory insufficiency eventually becomes irreversible

Efraim Racker coined the term “Warburg effect”, which refers to the aerobic glycolysis that occurs in cancer cells

Warburg clearly demonstrated that aerobic fermentation (aerobic glycolysis) is an effect, and not the cause, of insufficient respiration

all tumor cells that have been examined to date contain abnormalities in the content or composition of cardiolipin

The evidence supporting Warburg’s original theory comes from a broad range of cancers and is now overwhelming

respiratory insufficiency, arising from any number mitochondrial defects, can contribute to the fermentation metabolism seen in tumor cells.

data from the nuclear and mitochondrial transfer experiments suggest that oncogene changes are effects, rather than causes, of tumorigenesis

Normal mitochondria can suppress tumorigenesis, whereas abnormal mitochondria can enhance tumorigenesis

In addition to glucose, cancer cells also rely heavily on glutamine for growth and survival

Glutamine is anapleurotic and can be rapidly metabolized to glutamate and then to α-ketoglutarate for entry into the TCA cycle

Glucose and glutamine act synergistically for driving rapid tumor cell growth

Glutamine metabolism can produce ATP from the TCA cycle under aerobic conditions

Amino acid fermentation can generate energy through TCA cycle substrate level phosphorylation under hypoxic conditions

Hif-1α stabilization enhances aerobic fermentation

targeting glucose and glutamine will deprive the microenvironment of fermentable fuels

Although Warburg’s hypothesis on the origin of cancer has created confusion and controversy [37, 38, 39, 40], his hypothesis has never been disproved

Warburg referred to the phenomenon of enhanced glycolysis in cancer cells as “aerobic fermentation” to highlight the abnormal production of lactic acid in the presence of oxygen

Emerging evidence indicates that macrophages, or their fusion hybridization with neoplastic stem cells, are the origin of metastatic cancer cells

Radiation therapy can enhance fusion hybridization that could increase risk for invasive and metastatic tumor cells

Kamphorst et al. in showing that pancreatic ductal adenocarcinoma cells could obtain glutamine under nutrient poor conditions through lysosomal digestion of extracellular proteins

It will therefore become necessary to also target lysosomal digestion, under reduced glucose and glutamine conditions, to effectively manage those invasive and metastatic cancers that express cannibalism and phagocytosis.

Previous studies in yeast and mammalian cells show that disruption of aerobic respiration can cause mutations (loss of heterozygosity, chromosome instability, and epigenetic modifications etc.) in the nuclear genome

The somatic mutations and genomic instability seen in tumor cells thus arise from a protracted reliance on fermentation energy metabolism and a disruption of redox balance through excess oxidative stress.

According to the mitochondrial metabolic theory of cancer, the large genomic heterogeneity seen in tumor cells arises as a consequence, rather than as a cause, of mitochondrial dysfunction

A therapeutic strategy targeting the metabolic abnormality common to most tumor cells should therefore be more effective in managing cancer than would a strategy targeting genetic mutations that vary widely between tumors of the same histological grade and even within the same tumor

Tumor cells are more fit than normal cells to survive in the hypoxic niche of the tumor microenvironment

Hypoxic adaptation of tumor cells allows for them to avoid apoptosis due to their metabolic reprograming following a gradual loss of respiratory function

The high rates of tumor cell glycolysis and glutaminolysis will also make them resistant to apoptosis, ROS, and chemotherapy drugs

Despite having high levels of ROS, glutamate-derived from glutamine contributes to glutathione production that can protect tumor cells from ROS

It is clear that adaptability to environmental stress is greater in normal cells than in tumor cells, as normal cells can transition from the metabolism of glucose to the metabolism of ketone bodies when glucose becomes limiting

Mitochondrial respiratory chain defects will prevent tumor cells from using ketone bodies for energy

glycolysis-dependent tumor cells are less adaptable to metabolic stress than are the normal cells. This vulnerability can be exploited for targeting tumor cell energy metabolism

In contrast to dietary energy reduction, radiation and toxic drugs can damage the microenvironment and transform normal cells into tumor cells while also creating tumor cells that become highly resistant to drugs and radiation

Drug-resistant tumor cells arise in large part from the damage to respiration in bystander pre-cancerous cells

Because energy generated through substrate level phosphorylation is greater in tumor cells than in normal cells, tumor cells are more dependent than normal cells on the availability of fermentable fuels (glucose and glutamine)

Ketone bodies and fats are non-fermentable fuels

Although some tumor cells might appear to oxidize ketone bodies by the presence of ketolytic enzymes [181], it is not clear if ketone bodies and fats can provide sufficient energy for cell viability in the absence of glucose and glutamine

Apoptosis under energy stress is greater in tumor cells than in normal cells

A calorie restricted ketogenic diet or dietary energy reduction creates chronic metabolic stress in the body

. This energy stress acts as a press disturbance

Drugs that target availability of glucose and glutamine would act as pulse disturbances

Hyperbaric oxygen therapy can also be considered another pulse disturbance

The KD can more effectively reduce glucose and elevate blood ketone bodies than can CR alone making the KD potentially more therapeutic against tumors than CR

Campbell showed that tumor growth in rats is greater under high protein (>20%) than under low protein content (<10%) in the diet

Protein amino acids can be metabolized to glucose through the Cori cycle

The fats in KDs used clinically also contain more medium chain triglycerides

Calorie restriction, fasting, and restricted KDs are anti-angiogenic, anti-inflammatory, and pro-apoptotic and thus can target and eliminate tumor cells through multiple mechanisms

Ketogenic diets can also spare muscle protein, enhance immunity, and delay cancer cachexia, which is a major problem in managing metastatic cancer

GKI values of 1.0 or below are considered therapeutic

The GKI can therefore serve as a biomarker to assess the therapeutic efficacy of various diets in a broad range of cancers.

It is important to remember that insulin drives glycolysis through stimulation of the pyruvate dehydrogenase complex

The water-soluble ketone bodies (D-β-hydroxybutyrate and acetoacetate) are produced largely in the liver from adipocyte-derived fatty acids and ketogenic dietary fat. Ketone bodies bypass glycolysis and directly enter the mitochondria for metabolism to acetyl-CoA

Due to mitochondrial defects, tumor cells cannot exploit the therapeutic benefits of burning ketone bodies as normal cells would

Therapeutic ketosis with racemic ketone esters can also make it feasible to safely sustain hypoglycemia for inducing metabolic stress on cancer cells

ketone bodies can inhibit histone deacetylases (HDAC) [229]. HDAC inhibitors play a role in targeting the cancer epigenome

Therapeutic ketosis reduces circulating inflammatory markers, and ketones directly inhibit the NLRP3 inflammasome, an important pro-inflammatory pathway linked to carcinogenesis and an important target for cancer treatment response

Chronic psychological stress is known to promote tumorigenesis through elevations of blood glucose, glucocorticoids, catecholamines, and insulin-like growth factor (IGF-1)

In addition to calorie-restricted ketogenic diets, psychological stress management involving exercise, yoga, music etc. also act as press disturbances that can help reduce fatigue, depression, and anxiety in cancer patients and in animal models

Ketone supplementation has also been shown to reduce anxiety behavior in animal models

This physiological state also enhances the efficacy of chemotherapy and radiation therapy, while reducing the side effects

lower dosages of chemotherapeutic drugs can be used when administered together with calorie restriction or restricted ketogenic diets (KD-R)

Besides 2-DG, a range of other glycolysis inhibitors might also produce similar therapeutic effects when combined with the KD-R including 3-bromopyruvate, oxaloacetate, and lonidamine

A synergistic interaction of the KD diet plus radiation was seen

It is important to recognize, however, that the radiotherapy used in glioma patients can damage the respiration of normal cells and increase availability of glutamine in the microenvironment, which can increase risk of tumor recurrence especially when used together with the steroid drug dexamethasone

Poff and colleagues demonstrated that hyperbaric oxygen therapy (HBOT) enhanced the ability of the KD to reduce tumor growth and metastasis

HBOT also increases oxidative stress and membrane lipid peroxidation of GBM cells in vitro

The effects of the KD and HBOT can be enhanced with administration of exogenous ketones, which further suppressed tumor growth and metastasis

Besides HBOT, intravenous vitamin C and dichloroacetate (DCA) can also be used with the KD to selectively increase oxidative stress in tumor cells

Recent evidence also shows that ketone supplementation may enhance or preserve overall physical and mental health

Some tumors use glucose as a prime fuel for growth, whereas other tumors use glutamine as a prime fuel [102, 186, 262, 263, 264]. Glutamine-dependent tumors are generally less detectable than glucose-dependent under FDG-PET imaging, but could be detected under glutamine-based PET imaging

GBM and use glutamine as a major fuel

Many of the current treatments used for cancer management are based on the view that cancer is a genetic disease

Emerging evidence indicates that cancer is a mitochondrial metabolic disease that depends on availability of fermentable fuels for tumor cell growth and survival

Glucose and glutamine are the most abundant fermentable fuels present in the circulation and in the tumor microenvironment

Low-carbohydrate, high fat-ketogenic diets coupled with glycolysis inhibitors will reduce metabolic flux through the glycolytic and pentose phosphate pathways needed for synthesis of ATP, lipids, glutathione, and nucleotides

the ketogenic diet may inhibit cancer progression in part by indirect dietary energy restriction

KD with HBO2T. Combining these therapies nearly doubled survival time in mice with metastatic cancer,

low carbohydrate or ketogenic diets promote weight loss in overweight individuals, they are also known to spare muscle wasting during conditions of energy restriction and starvation

dietary-induced therapeutic ketosis in a cancer patient would prevent muscle wasting similarly as it does with athletes undergoing intense exercise

when given as an adjuvant treatment to advanced cancer patients, the KD improves quality of life and enhances the efficacy of chemotherapy treatment in the clinic

Previous studies showed that GBM survival and tumor growth was correlated with blood glucose levels

Evidence indicates that glioma cells cannot effectively use ketone bodies for energy due to defects in the number, structure, and function of their mitochondria

The accuracy of the GKI as a predictor for therapeutic efficacy, however, is better when ketone bodies are measured from the blood than when measured from the urine

A reduction of glucose-driven lactic acid fermentation would not only increase tumor cell apoptosis, but would also reduce inflammation and edema in the tumor microenvironment thus reducing tumor cell angiogenesis and invasion

Besides serving as a metabolic fuel for GBM, glutamine is also an essential metabolite for normal immune cells

therapies that inhibit glutamine availability and utilization must be strategically employed to avoid inadvertent impairment of immune cell functions

we used the non-toxic green tea extract, EGCG, and chloroquine in an attempt to limit glutamine availability to the tumor cells

EGCG is thought to target the glutamate dehydrogenase activity that facilitates glutamine metabolism in GBM cells

Chloroquine, on the other hand, will inhibit lysosomal digestion thus restricting fermentable amino acids and carbohydrates from phagocytosed materials in the tumor microenvironment

HBOT to increase oxidative stress in the tumor cells

As glucose and glutamine fermentation protect tumor cells from oxidative stress, reduced availability of these metabolites under ketosis could enhance the therapeutic action of HBOT, as we recently described

Prior to subtotal tumor resection and standard of care (SOC), the patient conducted a 72-h water-only fast

Following the fast, the patient initiated a vitamin/mineral-supplemented ketogenic diet (KD) for 21 days that delivered 900 kcal/day

KD (increased to 1,500 kcal/day at day 22

the patient received metformin (1,000 mg/day), methylfolate (1,000 mg/day), chloroquine phosphate (150 mg/day), epigallocatechin gallate (400 mg/day), and hyperbaric oxygen therapy (HBOT) (60 min/session, 5 sessions/week at 2.5 ATA)

Biomarkers showed reduced blood glucose and elevated levels of urinary ketones with evidence of reduced metabolic activity (choline/N-acetylaspartate ratio) and normalized levels of insulin, triglycerides, and vitamin D

This is the first report of confirmed GBM treated with a modified SOC together with KMT and HBOT, and other targeted metabolic therapies

Glioblastoma multiforme (GBM) is the most common and malignant of the primary adult brain cancers

less than 20% of younger adults generally survive beyond 24 months

glucose and glutamine are the primary fuels that drive the rapid growth of most tumors including GBM

Glucose drives tumor growth through aerobic fermentation (Warburg effect), while glutamine drives tumor growth through glutaminolysis

The fermentation waste products of these molecules, i.e., lactic acid and succinic acid, respectively, acidify the tumor microenvironment thus contributing further to tumor progression

Glucose and glutamine metabolism is also responsible for the high antioxidant capacity of the tumor cells thus making them resistant to chemo- and radiotherapies

The reliance on glucose and glutamine for tumor cell malignancy comes largely from the documented defects in the number, structure, and function of mitochondria and mitochondrial-associated membranes

These abnormalities cause the neoplastic GBM cells to rely more heavily on substrate level phosphorylation than on oxidative phosphorylation for energy

dexamethasone not only increases blood glucose levels but also increases glutamine levels through its induction of glutamine synthetase activity

Calorie restriction and restricted KD are anti-angiogenic, anti-inflammatory, anti-invasive, and also kill tumor cells through a proapoptotic mechanism

Evidence also shows that therapeutic ketosis can act synergistically with several drugs and procedures to enhance cancer management improving both progression free and overall survival

hyperbaric oxygen therapy (HBOT) increases oxidative stress on tumor cells especially when used alongside therapies that reduce blood glucose and raise blood ketones

The glutamine dehydrogenase inhibitor, epigallocatechin gallate (EGCG) is also proposed to target glutamine metabolism

the protein supply consumed during a KD “preserves,” as demonstrated, lean body mass

The importance of glycerol as a glucose source increases progressively during ketosis; in fact, glycerol passes from supplying 16% of total glucose to an average of 60% after many days (>7 d) of complete fasting (from 38% in lean individual to 79% in the obese).

The possible reasons for the effectiveness of KD for weight loss may be listed as follows, in order of evidence, strongest first: Figure 3Image Tools 1. Appetite reduction: protein satiety, effects on appetite-related hormones such as ghrelin, and possibly a sort of direct appetite-blocking effect of KB 2. Reduced lipogenesis and increased fat oxidation 3. A reduction in respiratory quotient may indicate a greater metabolic efficiency in fat oxidation 4. A thermic effect of proteins and increased energy usage by gluconeogenesis

all data regarding biochemical and molecular mechanisms suggest that it is very difficult to increase muscle mass during a KD; use of which really should be limited to the few days immediately before competition in bodybuilding.

a long-term KD can interfere with some muscle hypertrophy mechanisms and this could be counterproductive if the aim of the athlete is to gain muscle mass