Starving cancer by fasting and ketogenic diet, a review

RECOMMENDED CANCER, STARVING DIET, MACROPHAGES

Starving cancer by fasting and ketogenic diet, a review

“In oncology, the Warburg effect is the observation that most cancer cells predominantly produce energy by a high rate of glycolysis followed by lactic acid fermentation in the cytosol,^[4]^[5] rather than by a comparatively low rate of glycolysis followed by oxidation of pyruvate in mitochondria as in most normal cells.^[6]^[7]^[8] The latter process is aerobic (uses oxygen). Malignant, rapidly growing tumor cells typically have glycolytic rates up to 200 times higher than those of their normal tissues of origin; this occurs even if oxygen is plentiful.

Glycolysis is an oxygen independent metabolic pathway, meaning that it does not use molecular oxygen (i.e. atmospheric oxygen) for any of its reactions. However the products of glycolysis (pyruvate and NADH + H⁺) are sometimes metabolized using atmospheric oxygen. When molecular oxygen is used for the metabolism of the products of glycolysis the process is usually referred to as aerobic, whereas if no oxygen is used the process is said to be anaerobic.^[5] Thus, glycolysis occurs, with variations, in nearly all organisms, both aerobic and anaerobic.

Otto Warburg postulated this change in metabolism is the fundamental cause of cancer,^[9] a claim now known as the Warburg hypothesis. Today, mutations in oncogenes and tumor suppressor genes are thought to be responsible for malignant transformation, and the Warburg effect is considered to be a result of these mutations rather than a cause.^[10]^[11] https://en.wikipedia.org/wiki/Warburg_effect

Adam Kapelner, Matthew Vorsanger

Starvation of cancer via induced ketogenesis and severe hypoglycemia

Adam Kapelner and Matthew Vorsanger Published by Cornell University Library.

At http://arxiv.org/abs/1407.7622--entire, submitted on 29 Jul 2014 (v1),published Dec 8, 2014. Last revlso at http://www.medical-hypotheses.com/article/S0306-9877(14)00398-3/abstract and at http://www.mathpubs.com/detail/1407.7622v2/Starvation-of-Cancer-via-Induced-Ketogenesis-and-Severe-Hypoglycemia PDF FULL FREE at http://arxiv.org/pdf/1407.7622.pdf and on Desk top folder, med UCSD.

Abstract Neoplasms [tumors] are highly dependent on glucose as their substrate for energy production and are generally not able to catabolize other fuel sources such as ketones and fatty acids. Thus, removing access to glucose has the potential to starve cancer cells and induce apoptosis. Unfortunately, other body tissues are also dependent on glucose for energy under normal conditions. However, in human starvation (or in the setting of diet-induced ketogenesis), the body “keto-adapts” and glucose requirements of most tissues drop to almost nil. Exceptions include the central nervous system (CNS) and various other tissues which have a small but obligatory requirement of glucose. Our hypothesized treatment takes keto-adaptation as a prerequisite. We then propose the induction of severe hypoglycemia by depressing gluconeogenesis while administering glucose to the brain. Although severe hypoglycemia normally produces adverse effects such as seizure and coma, it is relatively safe following keto-adaptation. [the coma from too much insulin in diabetics occurs because their body hasn’t had time to switch to fat metabolism, not a problem with induction phase and thereby raise serum glucose to the normal level. In the full article low levels of serum glucose are obtained during long-term fasting, blew that from KD (ketogenic diet) without serious side effects—jk.] We hypothesize that our therapeutic hypoglycemia treatment has potential to rapidly induce tumor cell necrosis.

1 Introduction:

In 1924, Otto Heinrich Warburg's Nobel-prize winning research demonstrated that neoplastic cells rely on anaerobic glycolysis for their metabolic needs. Almost a century later, the results and implications of his findings are still hotly debated. It is now accepted that most tumors derive the vast majority of their energy from glucose. This major weakness is an attractive target for therapeutic intervention. However, basic physiology dictates that normal cells would also be starved by severe hypoglycemia. As such, targeting cancer by exploiting this metabolic weakness has not been proven fruitful to date.1 In fact, cancer treatment has moved away from broadly cytotoxic modalities towards highly targeted therapies (Aggarwal, 2010). Treatments of choice include monoclonal antibodies, tyrosine kinase inhibitors, and induction of specific immune responses as well as others. In this paper, we reexamine the possibility of therapeutic hypoglycemia as an antineo-plastic treatment while simultaneously delivering glucose to the body tissues that require it.

Our main hypothesis is that the alterations in metabolism that occur in the starvation state, namely neurologic adaptation to hypoglycemia, provide a means of safely inducing hypoglycemia. Of course, this proposal is not mutually exclusive with other standard treatments such as radiation, chemotherapy and dietary supplementation. The outline of the paper is as follows. Section 2 provides background on cancer cell metabolism and reviews the known cytotoxic effects of hypoglycemia on cancerous cells. Here, we justify the assumptions needed for our hypothesized treatment from the literature. The next two subsections are prerequisites for understanding the implementation of our hypothesized treatment. Section 3.1 discusses the body's theoretical minimum glucose requirements during starvation as well as the concept of tissue keto-adaptation. Section 3.2 discusses ketogenic dieting as a viable alternative to starvation while retaining body-wide minimal glucose needs. We outline our severe hypoglycemia therapy in detail in Section 3.3.

Section 4 concludes and discusses further extensions as well as potential concerns.

Background:

Cancer is the result of multiple changes in the delicate balance of cell function. The root cause of neoplastic transformation is still under serious debate. There are many theories: cancer is primarily a genetic disease (Vogelstein et al., 2013), cancer is a disease of aberrant metabolism due to dysfunctional respiration in malfunctioning mitochondria (Seyfried and Shelton, 2010), cancer is due to overproduction of reactive oxygen species[1] (Oleksyszyn et al., 2014), as well as others [such as fusion transfer of the mitochondria to a macrophage, Seyfried].

Regardless of the cause, the majority of neoplastic cells feature an aberrant glucose metabolism, first disvocered by Warburg et al (1924) and now known as the “Warburg Effect”. [NORMAL CELLS METABOLIZE GLUCOSE IN TWO STEPS]. First, glucose is broken down to created pyruvate and a small amount of adenosine triphosphate in the cytosol (glycolysis) [outside of the Mitochondria]. Second, pyruvate is shuttled into mitochondria where it is fully oxidized to water and carbon dioxide in the Krebs cycle [Krebs did this research in Warburg’s laboratory]. Even with enough oxygen, cancer cells do not seem to advance beyond cytosolic glycolysis to employ the vastly more efficient (by factor of 17 : 1) oxidative phosphorylation. Instead, they divert their pyruvate to produce lactic acid. This is oxymoronically known as “aerobic glycolysis;” cancer cells ferment even in conditions of normoxia [this sentence means that metabolism proceeds without oxygen, and the term aerobic is the opposite of what occurs, like giant shrimp; normoxia means hypoxia, without oxygen ]. A potential cause of this aberrant metabolism is that cancer cells only have a fraction of the mitochondria available to normal cells and these mitochondria are structurally defective (see a review by Pedersen, 1977 and see Elliott and Barnett, 2011 for an electron microscopy study of mitochondria from breast carcinoma). Others say the cause is damaged glycolysis regulation (Koppenol et al., 2011). Regardless, “all roads to the origin and progression of cancer pass through the mitochondria" and the hallmark of cancer is oxidative phosphorylation to varying degrees (Seyfried et al., 2014). This implies that cancer cells do not have access to non-glycolytic fuels that demand full oxidative combustion in the Krebs cycle, namely fatty acids and the ketone bodies beta-hydroxybutyrate and acetoacetate (Holm et al., 1995, Sawai et al., 2004), two substrates that are key players in our hypothesized treatment. Chang et al (2013) demonstrated that glioma cells [neuro cells, glial or glia cells, non-neuronal cells that maintain homeostasis in the nervous system] in their investigation lack enzymes that break down ketones. Such evidence may explain why introduction of healthy mitochondria into cancer cell cytoplasm halts carcinogenesis (see Seyfried, 2012, Chapter 11 for a review of these studies).

The relevant point to our hypothesis is that glucose is the predominant energy substrate for most cancers (Gullino et al. 1967) with glycolytic rates [metabolism of glucose] 8-200 times higher than normal tissues (Phelps, 2004, Chapter 5) while producing about 10% more ATP than normal cells [very inefficient] (Koppenol et al. 2011). Cancer has a large fuel requirement due to its high proliferation rate and large need for antioxidants. In addition, high glucose consumption is necessary for intermediaries required in biosynthetic pathways: ribose for nucleotides; glycerol, pyruvate, and citrate for lipids; amino acids and nicotinamide adenine dinucleotide phosphate (NADPH) via pentose phosphate pathway (Dederardinis et al., 2008)

Glycolysis being the exclusive source of energy in cancer is hotly debated and may not be true of all cancers throughout their lifespan; tumors may have varied bio-energetic profiles. [Pharma’s KOLs (key opinion leaders) do tobacco science and debate the merits of KD; thus they promote drug treatments.] They may be glycolytic and/or oxidative (Jelluma et al., 2006; Moreno-Sanchez et al., 2007; Martinez-Outschoorn et al., 2011; Jose et al., 2011; Carracedo et al., 2013). For the purpose of this article, we address the majority of neoplasms which the consensus holds are exclusively glycolytic. We await future research that will elucidate when and in which cancer lines our hypothesize treatment is most applicable.

Thus cancer should be particularly vulnerable to glucose/glycolytic substrate deprivation. Starving cancer from glucose is not a novel idea; proposals to treat cancer via serum hypoglycemia date back to an editorial in the New York Times (1887) and are abundant in the recent literature (Woolf and Scheck, 2014; Simone et al., 2013; Fine et al., 2012, 2008; Seyfried et al., 2008; Mavropoulos et al., 2006; Kim et al., 1978). Another idea would be to inhibit glycolysis (e.g. Ganapathy-Kanniappan et al., 2010) but this is not the strategy we propose due to its more universal cytotoxicity [major side effects].

Even though the idea of cancer starvation is commonplace, there are no well-designed studies evaluating this premise…. Financial concerns are also a likely explanation.… With the time and resources needed to produce a high-quality clinical trial, it is unlikely that therapeutic hypoglycemia would produce an adequate return-on-investment for a pharmaceutical company…. There are many uncontrolled studies that are optimistic. For example, Zuccoli et al. (2010) details the account of a woman who had spontaneous remission (i.e. sudden disappearance of cancer) of glioblastoma multiforme after two months on a diet formulated to lower serum glucose. Niakan (2010) concluded that over 1,000 similar spontaneous remissions are most likely due to hypoglycemia and hypoxia [lack of oxygen] (arguably a direct consequence of the hypoglycemia).

Pre-clinical animal studies demonstrate promising results by cutting cancer's nutrient supply (Mukherjee et al., 2002, 2004; Zhou et al., 2007; Otto et al., 2008; Mavropoulos et al., 2009; Shelton et al., 2010; Stafford et al., 2010; De Lorenzo et al., 2011; Sivananthan, 2013; Jiang and Wang, 2013). However, there are some studies that are inconclusive (e.g. Masko et al., 2010). However, there are some studies that are inconclusive (e.g. Masko et al.,2010) [probably a pharma’s KOLs].

There are many creative in-vitro studies of glucose starvation. In Demetrakopoulos et al. (1978), tumor cells were found to be highly sensitive to glucose deprivation. Spitz et al. (2000) found that glucose withdrawal induces cytotoxicity in transformed broblasts and colorectal cells, which they argue is the result of oxidative stress. Buzzai et al. (2005) demonstrated that activation of the commonly expressed oncogene Akt prevents cancer cells from metabolizing non-glycolytic substrates. Jelluma et al. (2006) perfomed the first study of glucose withdrawal on glioblastoma multiforme cells and found 90% cell death in 24 hours. The death was not due to ATP depletion and could be rescued by a free radical scavenger, thereby lending credence to the oxidative stress theory. Aykin-Burns et al. (2009) demonstrated that glucose deprivation can induce cytotoxicity in human breast cancer cells and colon cancer cells in-vivo. They argue these results are due to cancer being unable to synthesize reducing agents such as NADPH and pyruvate which are needed en masse for detoxication of high concentrations of free radicals due to mitochondrial abnormalities. Li et al. (2010) observed growth inhibition and apoptosis in lung broblasts after glucose restriction and Priebe et al. (2011) demonstrated cell death in ovarian cancer. Also, Graham et al. (2012) demonstrated that glucose withdrawal slows the proliferation, induces hyperthermia, and possibly induces cancer cell death in four gliobastoma cell lines.

Our proposal is a natural extension of previous cancer starvation proposals. We propose a ketogenic diet which allows for the safe induction of severe hypoglycemia via gluconeogenesis attenuation. The serum levels we propose are lower than have ever been proposed in the past and we do so in order to starve cancer cells rapidly. We now turn to detailing this therapy.

[1] This is consistent with damage mitochondria because the major source of ROS (reactive oxygen species is form the production of ATP in the mitochondria, See Endogenous ROS in the Wikipedia article.

3 Our hypothesis

The next two sections provide background material about human starvation and ketogenic dieting that is necessary for understanding our hypothesized treatment which we detail in Section 3.3

3.1 Starvation: Minimizing the Body's Glucose Needs

The body’s glucose requirements are minimized during periods of starvation, which constitutes drastic transformation in the body’s energy metabolism. Broadly speaking starvation has five stages which are outlined in the Table 1 below.

Normally by the end of the first day, hepatic glycogen stores are depleted and the liver (and to a lesser extent, the kidneys) begin to produce glucose from pyruvate, glycerol and amino acids. The vast majority of tissues in the body (such as skeletal muscle, the heart, and most organs) are facultative in their choice of substrate for energy production. During this period of glucose scarcity, they cut their glucose metabolism and increase their metabolism of free fatty acids (FFAs). Starvation even at this early stage forces body tissues to switch from glycolysis to lipid oxidation for their energy needs. The ketone bodies Beta OHB, acetoacetate and acetone are always present in the blood, but after a few days of starvation they begin to be produced in large quantities in the liver. Most tissues of the body can metabolize ketones (with the exception of acetone).

Stages of starvation	Physiological description	Time period
1	Gastrointestinal absorption	<1
2	Glycogenolysis	<2
3	Gluconeogenesis	>2
4	Ketosis	>3
5 (prolonged)	Decreased gluconeogenesis and increased cerebral ketone consumption	>14

Table 1. The five stages of starvation from the time of last ingestion (reprinted from Cahill, 1983, page 2).

Of special interest is stage 5--prolonged starvation of two weeks and longer. Cells have long since cut their uptake of glucose but now also cut their uptake of ketones. This change, coupled with increased blood-brain-barrier permeability of ketones (Morris, 2005) we will call keto-adaptation." During stage 5, most cells rely purely on FFAs for their metabolic requirements (Robinson and Williamson, 1980). However, some tissues still retain a need for glucose even after keto-adaptation. The largest consumer is the brain and CNS, whose health is vital to the success of our hypothesis.

How much glucose does the brain need? A typical brain glucose requirement (Cahill, 1970, Figure 1). This is a preferential utilization but not an obligatory utilization. This point is crucial to our hypothesis. During keto-adaptation, the brain glucose requirement drops to approximately 44 g/day (Cahill, 1970, Figure 5).[1]

What supplies the energy that this difference of approximately 100 g/day of glucose previously supplied? [The brain consumes about 150 g/day of glucose.] The ketone bodies -OHB and acetoacetate in a 6:1 proportion (Owen et al., 1967, Table 5). Note that the brain does not metabolize FFAs (Owen et al., 1967, Table 4). In stage 5 starvation, ketone blood levels surge to 2.5-9.7 mmol/L which are in contrast to a negligible level of .01 mmol/L in non-starving subjects. The brain will readily use ketone bodies if they are available even in non-fasting periods, but under this condition ketone usage is negligible (Sokolo , 1973). Morris (2005) suspects that the brain's ketone metabolism was evolutionarily developed to ensure survival in times of glucose being scare. Cahill (1970) suspects that other body tissues slash their ketone consumption in favor of FFA's to ensure adequate substrate for the brain. Further, Cahill and Veech (2003).

The fuel metabolism of stage 5 starvation is illustrated in Figure 1. Of special interest is the inventory of the sources of gluconeogenesis that provide the 44 g/day CNS requirement: stored triacylglycerols (15g), amino acids taken from muscle tissue and to a lesser extent other tissues (20g), and pyruvate / lactate (14g), which is the end product of anaerobic glycolysis (thus about a third of the glucose during starvation burned by the CNS is recycled back into glucose via the Cori cycle).

The figure of 24 hours Basal Metabolism (~`,500 CAL) won’t copy

Figure 1: Fuel sources and sinks in the daily metabolism of Stage 5 starvation assuming a

1500 calorie resting metabolism (inspired by Cahill, 1970, Figure 5).

Starvation can be a useful tool to minimize glucose needs in all but a few body tissues. Fasting, while relatively safe (Stewart and Fleming, 1973), is not only unpleasant but leads to muscle wasting and weight loss, both of which are serious concerns in cancer patients. How do we minimize the body's glucose needs while avoiding these undesired effects? We turn to a solution in the next section.

3.2 Keto-adaptation via the 4:1 Ketogenic Diet

A means to emulate the metabolic conditions of starvation while still ingesting food is the same engineering problem faced in the 1920's by the expert childhood epileptologist Dr. Russel M. Wilder. He observed that short-term starvation was therapeutic for children with intractable epilepsy, but obviously impractical as a long-term solution. He innovated the “ketogenic diet" (KD) that mimics the characteristic starvation metabolism we outlined in Section 3.1. It is still used today to reduce seizures (for an historical account and a recent clinical trial, see Neal et al., 2008).

[RM] Wilder's KD is a high fat, low protein and very low carbohydrate diet (McDonald, 1998). In what is called the “4:1 KD," carbohydrate must be limited to 20 g/day (the amount the muscle tissue provides during prolonged starvation) and protein must be limited to an amount to offset normal (non-starvation) protein turnover, estimated at about 25 g/day for a 70kg person (National Research Council (US) Food & Nutrition Board, 1989). Any additional protein has the potential to be gluconeogenic and thereby should be avoided. All other calories must be supplied by fats.⁵ Commercial formulas for this diet are readily available. [High fat, butter on cellar/lettice with 25 gm of protein diet for fast—Jk idea].

Are the physiological markers in a prolonged 4:1 KD exactly the same as markers under prolonged starvation? Depending on the macronutrient proportions, serum glucose can be slightly higher and ketone levels slightly lower (Phinney et al., 1983). We assume that a 4:1 KD is equivalent to keto-adapted metabolism observed during prolonged starvation described in Section 3.1: glucose uptake minimization, increased cerebral ketone uptake, and exclusive use of FFAs for energy production in every other tissue in the body. Thus, a KD can achieve starvation metabolism adaptation without the unpleasant side effects of hunger and muscle loss.

Simone et al. (2013) also reviews other benefits of the KD such as muscle sparing and possible even muscle synthesis which can be beneficial for cancer patients with risk of cachexia. The KD is generally well-tolerated with minimal side effects such as constipation, salt loss, mild acidosis and increased incidence of kidney stones, when employed chronically" and has been demonstrated to be safe even in patients with advanced cancer (Schmidt et al., 2011). Kossoff et al (2007) reports on the longest duration of a KD: 21 years with virtually no side effects. There is also some evidence that ketones in their own right are directly toxic to cancer (Magee et al., 1979; Skinner et al., 2009; Fine et al., 2009) and can improve the immune system's ability to target cancer (Husain et al., 2013). This can be an added benefit of the KD that can work in tandem with our hypoglycemia strategy.

Our hypothesized treatment begins with a cancer patient being administered a 4:1 KD for more than 14 days to allow for keto-adaptation. Then our proposed acute treatment is begun. We turn to implementation details now.

3.3 Our Proposed Treatment

Section 2 discussed previous literature that experimented with both starvation and the KD for cancer therapy via glucose starvation. We believe these studies did not reduce serum glucose to levels sufficient to starve cancer. On a KD, “plasma glucose concentration fall only mildly, remaining in the normal range in normal-weight individuals ... [thus] ... simple tumor glucose starvation is therefore unlikely in humans" (Fine et al., 2008).

Serum glucose in prolonged starvation drops to about 65mg/dL (Cahill, 1970, Table 2) and the prolonged 4:1 KD can also result in a similar serum level, but it is unclear why further reduction in the blood glucose level should not be similarly well-tolerated after keto-adaptation.

In an adult, cerebral blood flow is approximately 750mL/min = 0.13 dL/s which implies 8.1mg/s of glucose can potentially be delivered to the brain. In Section 3.1, we noted that the brain has an obligatory requirement of 44 g/day = 0.51 mg/s6 which is only 6% of the glucose available at a serum concentration of 65 mg/dL. Although experiments evaluating the glucose extraction ratio in human subjects are limited, animal studies suggest that the brain is able to extract 40% of the serum glucose in the hypoglycemic state (McCall et al., 1986). Thus, we theorize that the body is being conservative. Serum glucose concentrations below the level where 0.51 mg/s can be actively transported into neurons for mere moments can result in CNS damage; 65 mg/dL is comfortably above this threshold.

We have evidence for this conjecture that keto-adapted subjects can survive on serum glucose much lower than 65mg/dL. Hypoglycemia has been reported in therapeutic fasting or starvation for over 100 years. Chakrabarty (1948) investigated 407 starvation cases in Bengal famine to find that 20 or so of them had chronic blood sugar below 40 mg/dL with no symptoms of hypoglycemia… We have evidence for this conjecture that keto-adapted subjects can survive on serum glucose much lower than 65mg/dL. Hypoglycemia has been reported in therapeutic fasting or starvation for over 100 years. Chakrabarty (1948) investing rated 407 starvation cases in the Bengal famine to and that 20 or so of them had chronic blood sugar below 40 mg/dL with no symptoms of hypoglycemia. Stewart and Fleming (1973) who supervised a world-record-setting 382-day therapeutic fast found that blood glucose became stable at 30 mg/dL, dropping intermittently to 20 mg/dL without symptoms. The most relevant evidence to our hypothesis is the observation of intentional acute hypoglycemia induction by Drenick et al. (1972) who keto-adapted obese patients via 45-60 days of starvation and then perfused insulin. Within the hour, they observed serum glucose as low as 9 mg/dL without acute hypoglycemic symptoms. Serum glucose this low would normally induce coma (which has even been observed with blood sugar as high as 40-49 mg/dL according to Ben-Ami et al., 1999, Figure 3).

Our plan is simple. After keto-adaptation with the 4:1 KD, we propose to acutely attenuate the serum glucose concentration to severely hypoglycemic levels such as observed in Drenick et al. (1972) on a patient-by-patient basis. Since insulin is required by cancer cells and fuels their metabolism (Iqbal et al., 2013) and also can impede ketogenesis, we choose not to induce hypoglycemia via insulin perfusion (as in Drenick et al., 1972), but instead propose the use of a gluconeogenesis inhibitor.

One possible inhibitor is the diabetic drug metformin which inhibits gluconeogensis indirectly. Metformin may have other anti-cancer effects (Jalving et al., 2010, Figure 3) and there is certainly supporting epidemiological evidence for metformin's therapeutic effect in cancer (Ben Sahra et al., 2010). For these reasons, it has been proposed for use in a hypothesized treatment similar to ours (see Oleksyszyn, 2011 and further in Oleksyszyn et al., 2014). However, metformin has many drawbacks. First, it is not a potent inducer of hypoglycemia in the doses that are normally administered. Metformin is also slow acting and not rapidly titratable. Additionally, the drug activates adenosine monophosphate activated protein kinase which may have other effects on metabolism under keto-adaptation (see Jalving et al., 2010, Figure 2). Lastly, supratherapeutic doses have been associated with fatal lactic acidosis.

Due to these shortcomings, we propose using a drug which is a pure liver-kidney gluco-neogenesis inhibitor. Luckily, these drugs have been investigated by the diabetes community where high endogenous glucose production is considered one of the characteristics of the disease and is therefore a therapeutic target.

There are many control points within gluconeogenesis. The unidirectional synthesis of fructose-6-phosphate from fructose-1,6-bisphospate is a prudent point to interrupt because it is removed from glycogenolysis and mitochondrial function (thus, it would have the fewest side effects). The synthesis is controlled via the rate-controlling enzyme fructose-1,6-bisphosphatase. Two inhibitors that have been clinically evaluated are named CS-917 and MB07803 (van Poelje et al., 2011). They have good safety profiles and can flexibly attenuate

gluconeogenesis to any desired level.

Returning to our discussion of the target level of hypoglycemia, we comment that we do not know the effective dose (ED) curves for serum glucose levels for tumor necrosis or the lethal dose (LD) curves for human body death after keto-adaptation. It is possible that a 9 mg/dL glucose concentration may be too high to be toxic for the cancer. If this proves to be the case, further hypoglycemia would need to be safely induced for treatment efficacy. We turn to this now.

Since the brain is the only tissue with an obligatory glucose requirement, we opt for direct perfusion of glucose into the brain intra-arterially via the carotid arteries at the rate necessary to provide minimum brain glycolytic needs. Perfusion of glucose directly to the brain has been performed successfully in rats (Borg et al., 1997) and baboons (Conway et al., 1969). Once the brain receives its required glucose, we propose an increase in the dose of gluconeogenic inhibitor drug to attenuate serum glucose to a negligible level which is safe enough for erythocytes, blood marrow and leukocytes to survive. The brain would perceive normoglycemia but everywhere outside of the brain the serum would be extremely hypoglycemic. If necessary, we can also perfuse _-OHB in tandem if there is risk that the level of ketosis is not sufficiently high for CNS metabolic needs. This protocol would require extensive proof-of-concept work in animal models before any attempt to undertake study in human subjects.

The reader may wonder if this strategy would be effective against brain cancer since the brain is still receiving glucose. Seyfried et al. (2003) reports data supporting that such a treatment may be effective since glucose uptake in brain cancers drops with lower serum glucose and that the cancer cannot metabolize ketones, which may even be toxic to them. How fast could this procedure induce tumor death? We echo Oleksyszyn et al. (2014), “we do not have any idea as to how deep hypoglycemia needs to be to trigger spontaneous remission." All estimates are drawn from data from in-vitro studies and thus are not generalizable to human prognoses. Spitz et al. (2000, Figure 2) reports between 55% and near 100% necrosis rates in three cancer lines within 48hr after total glucose deprivation. Complete withdrawal is not possible in the human body for reasons explained above and our treatment could deliver minimum serum levels estimated at 5 mg/dL.

[They propose direct infusion of glucose via the carotid artery and block glucose in the body with a drug similar to metformin. I doubt the need for this radical intervention.] This protocol would require extensive proof-of-concept work in animal models before any attempt to undertake study in human subjects. … Spitz et al. (2000, Figure 2) [in vitro] reports between 55% and near 100% necrosis rates in three cancer lines within 48hr after total glucose deprivation.

4 Discussion

We propose a therapy for starving cancer by inducing keto-adaptation followed by the induction of therapeutic hypoglycemia via gluconeogenesis inhibitor drugs. We then propose rescue cerebral glucose infusion through direct catheterization of the brains's blood supply. This would be followed by an increase of the gluconeogenic inhibitor drug to lower serum glucose even further in non-cerebral tissues.

A main concern is that each person is a unique metabolic entity" (Seyfried et al., 2014). The calculations presented throughout this manuscript are meant to be illustrative of an average person. For each individual, personalized dosing and administration schedules will require iterative fine-tuning.

Proper monitoring and its associated costs are a concern. Hypoglycemia is very risky but might not necessarily require the monitoring setting of an intensive care unit (patients with diabetic ketoacidosis are frequently treated with insulin infusion outside of the intensive care unit). Although the costs of the diet and the medications needed to induce hypoglycemia in our proposal might be far lower than the cost of novel chemotherapeutic agents, the cost of close monitoring may substantially erode this benefit.

There are several other concerns with speculative treatment. Cancer is heterogeneous and few predictors are currently available as to an individual tumor’s response to hypoglycemia. There is research suggesting that some cancer cells can make use of ketones and FFAs. Not all cancer lines proliferate rapidly and intense anabolism is not mandatory (Jose et al., 2011. Our hypothesized treatment would not work in such cancer lines. It is not known whether the proposed hypoglycemic levels can be sustained for long periods of time without symptoms. Starvation research suggests that hypoglycemia is safe in the long term, but these accounts documented serum levels many times above our proposed serum level and they were predominantly documented in obese subjects without cancer. An important consideration is whether keto-adaptation additionally protects against the neuro-hormal cardiovascular and electrophysiologic consequences of hypoglycemia (Frier et al., 2011). Additionally, glucose is not the sole nutritive substrate for cancer cells. For instance, glutamine can also serve as a major metabolite (Yuneva, 2008), as well as fermentation from other amino acids. There are times when the body is in need of glucose such as during inflammation and infection which limits the setting of our hypothesized treatment.

There is also a fair chance that our proposed treatment is more effective when provided in tandem with other therapies. For instance, Abdelwahab et al. (2012) demonstrated that brain cancer in mice was curtailed and did not recur with the simultaneous administration of the 4:1 KD and radiation therapy. Allen et al. (2013) demonstrated that the 4:1 KD enhances radio-chemo-therapy in mice models of lung cancer. See Klement and Champ (2014) for a discussion of how the KD can act synergistically with radiation therapy. Also, Lee et al. (2012) demonstrated that fasting enhances chemotherapy. Poff et al. (2013) demonstrated that hyperbaric oxygen therapy is enhanced by the KD.

Alternative adjuvant therapies may also be fruitful. For example, Majumdar et al. (2009) demonstrated that the combination of curcumin with resveratrol could be an effective therapy in colorectal cancer, Singh and Lai (2004) demonstrated cancer apoptosis from wormwood extract and Tin et al. (2007) demonstrated that astralagus saponins can inhibit colorectal cancer cell proliferation. There are many other such supplements that can be administeredsimultaneously with our hypoglycemia treatment.

Acknowledgements

We would like to thank Justin Bleich and Stephen Kapelner for helpful discussions and comments on this manuscript. We would like to thank Marie Le Pichon for illustrating Figure 1. Adam Kapelner acknowledges support from the National Science Foundation's Graduate Research Fellowship as well as support from the Simons Foundation Autism Research Initiative.

Taken from references and examined:

Eliot & Barnett 2011 not up 9/20/15) because of website modifications

Niakan on 1000 patients must obtain from UCSD http://onlinelibrary.wiley.com/doi/10.1111/j.1528-1167.2008.01853.x/pdf

Schmidt on KD diet terminal patient proved safety, but was too short to measure change in tumor size. Allow 70 gm carb/day. http://www.biomedcentral.com/content/pdf/1743-7075-8-54.pdf

Seyfried 2008 http://onlinelibrary.wiley.com/doi/10.1111/j.1528-1167.2008.01853.x/pdf

[1] It is not known if the average brain can do with less than 44 g/day of glucose. We assume that if the body can get away with providing less, it would do so. Why? Each gram of glucose conserved is one gram of protein conserved. Protein sparing is essential during starvation since protein is man's precious machinery vital to cellular structure and function. Depletion of these reserves can limit long-term survival even with massive lipid depots. This question can also be asked as follows: why are ketones unable to provide 100% of the brain's energy requirements? The answer is unknown and we posit two theories. First, there may be

incomplete -OHB and acetoacetate transport to all cells of the CNS (Morris, 2005). Second, -OHB and acetoacetate can only be converted to energy via oxidative phosphorylation in mitochondria; these organelles are scant in long and thin myelinated axons (Waxman et al., 1995, page 17). Here, we posit that some of the brain's energy production must default to glycolysis in the axoplasm.

References

1. Abdelwahab, M.G., Fenton, K.E., Preul, M.C., Rho, J.M., Lynch, A., Stafford, P. et al, The ketogenic diet is an effective adjuvant to radiation therapy for the treatment of malignant glioma. PloS One. 2012;7:e36197.