Successful application of dietary ketogenic metabolic therapy in patients with glioblastoma: a clinical study

Andreas Kiryttopoulos, Athanasios E. Evangeliou, Irene Katsanika, Ioannis Boukovinas, Nikolaos Foroglou, Basilios Zountsas, Angeliki Cheva, Vaios Nikolopoulos, Thomas Zaramboukas, Tomas Duraj, Thomas N. Seyfried, Martha Spilioti
Frontiers in Nutrition
Aristotle University of Thessaloniki

Table of Contents

Overall Summary

Study Background and Main Findings

This study was a prospective clinical trial involving 18 patients with newly diagnosed glioblastoma multiforme (GBM). The primary outcome was 3-year survival, with a benchmark of 3 years considered a success. Patients were divided into two groups based on adherence to a ketogenic diet for more than 6 months. The adherent group (n=6) had a 3-year survival rate of 66.7% (4 out of 6 patients), while the non-adherent group (n=12) had a 3-year survival rate of 8.3% (1 out of 12 patients). The difference between the groups was statistically significant (p < 0.05, X2 = 6.409). Secondary outcomes, such as ECOG scores and MRI evaluations, were mentioned but not fully reported in the results section. No interaction effects were explicitly analyzed. The study suggests a potential mechanistic link between ketogenic metabolic therapy and improved survival, based on the metabolic differences between normal brain cells and GBM cells, but this was not directly quantified.

Research Impact and Future Directions

The study demonstrates a statistically significant association between adherence to a ketogenic diet and improved 3-year survival in a small cohort of GBM patients. However, it is crucial to distinguish between correlation and causation. The study design does not allow for causal inferences due to its non-randomized nature and potential for confounding factors. Patients who were able to adhere to the diet may have differed systematically from those who did not, in ways that independently influenced survival.

The practical utility of the findings is promising but preliminary. The observed survival rates in the adherent group are higher than typically reported for GBM, suggesting a potential benefit of KMT. However, the small sample size and lack of a randomized control group limit the generalizability of these results. The findings should be considered within the context of existing research, which shows mixed results for KMT in GBM, with some studies suggesting potential benefits and others showing no significant effect.

Future research should focus on larger, randomized controlled trials to confirm these findings and determine the true efficacy of KMT. Clinicians should consider KMT as a potential adjunctive therapy for GBM, but only in the context of a well-designed clinical trial or with careful consideration of the potential benefits and risks. Patient education and support are crucial for improving adherence, and the diet should be implemented under the guidance of a qualified healthcare professional.

Critical unanswered questions remain, including the optimal ketogenic diet protocol, the mechanisms of action of KMT in GBM, and the potential for combining KMT with other therapies. The study's methodological limitations, particularly the non-randomized design and small sample size, fundamentally affect the conclusions that can be drawn. While the findings are suggestive of a potential benefit, they do not provide definitive evidence of KMT's efficacy in GBM.

Critical Analysis and Recommendations

Concise Summary of Key Findings (written-content)
The abstract concisely summarizes the key findings, highlighting the statistically significant difference in survival rates (66.7% vs 8.3%, p < 0.05) between adherent and non-adherent groups; This provides a quick overview of the main result; This is important for readers to quickly grasp the study's outcome; Readers can immediately understand the potential impact of the intervention.
Section: Abstract
Highlight Novelty (written-content)
The abstract does not explicitly state what is new about this study; This makes it harder for readers to quickly grasp its contribution to the field; Highlighting novelty is crucial for attracting readership and demonstrating the study's value; Adding a sentence about the unique aspects of the study (e.g., specific patient population, dietary protocol, or follow-up period) would improve the abstract's impact.
Section: Abstract
Explanation of Metabolic Rationale (written-content)
The introduction effectively explains the metabolic rationale behind KMT, highlighting differences between normal and GBM cells in utilizing glucose and ketones; This justifies the potential of KMT to selectively target cancer cells; Providing a clear scientific basis strengthens the study's hypothesis; Readers can understand why KMT is being investigated.
Section: Introduction
Explicitly State Study Novelty (written-content)
The introduction does not clearly differentiate this study's contribution from existing research; This makes it difficult to assess the study's unique value; Explicitly stating novelty is essential for justifying the research; Adding a sentence or paragraph outlining the specific aspects that make this study novel would improve its impact.
Section: Introduction
Clear Study Design and Criteria (written-content)
The methods section clearly outlines the study design as a prospective study and specifies inclusion/exclusion criteria; This enhances reproducibility and defines the target population; Clear methodology is crucial for assessing the study's validity; Other researchers can replicate the study and compare results.
Section: Materials and methods
Clarify Objective Adherence Assessment (written-content)
The methods section lacks detail on how adherence to the ketogenic diet was objectively assessed beyond self-reported measurements; This weakens the validity of the study's conclusions regarding adherence; Objective measures are crucial for ensuring the accuracy of the primary outcome; Describing the process for verifying self-reported data (e.g., dietician follow-up, food diaries) would strengthen the study's rigor.
Section: Materials and methods
Clear Presentation of Main Result (written-content)
The results section clearly presents the main result: 66.7% 3-year survival in the adherent group vs. 8.3% in the non-adherent group, with statistical significance (p < 0.05); This directly addresses the study's primary outcome; Clear presentation of key findings is essential for communicating the study's impact; Readers can easily understand the magnitude of the observed difference.
Section: Results
Fully Characterize Outcomes of Non-Adherent Group (written-content)
The results section does not fully characterize the outcomes of the non-adherent group beyond overall survival; This limits the reader's ability to fully evaluate the intervention's effects; Reporting all relevant results, even negative ones, is crucial for transparency and avoiding bias; Including a more detailed summary of outcomes for the non-adherent group (e.g., range of survival times, ECOG scores) would provide a more complete picture.
Section: Results
Contextualization of Findings (written-content)
The discussion contextualizes the findings by comparing survival rates to non-adherent patients and historical controls, highlighting the promising potential of KMT; This provides a broader perspective on the study's results; Comparing to existing data is essential for assessing the significance of the findings; Readers can understand how this study fits within the larger body of research.
Section: Discussion
Expand Discussion of Limitations (written-content)
The discussion does not adequately address the study's limitations, particularly the non-randomized design and potential for selection bias; This limits the ability to draw causal inferences; A robust discussion of limitations is crucial for interpreting the findings and guiding future research; Expanding the discussion to include a more in-depth analysis of potential confounding factors and biases would strengthen the paper's conclusions.
Section: Discussion

Section Analysis

Abstract

Key Aspects

Strengths

Suggestions for Improvement

Introduction

Key Aspects

Strengths

Suggestions for Improvement

Non-Text Elements

FIGURE 1 (A) Simplified scheme of glucose and ketone metabolism in a normal...
Full Caption

FIGURE 1 (A) Simplified scheme of glucose and ketone metabolism in a normal brain cell.

Figure/Table Image (Page 3)
FIGURE 1 (A) Simplified scheme of glucose and ketone metabolism in a normal brain cell.
First Reference in Text
Glucose and ketone metabolism in normal and cancer cells is illustrated in Figures 1A, B, 2A, B.
Description
  • Overview of glucose and ketone metabolism: Figure 1A illustrates the metabolic processes within a normal brain cell, focusing on glucose and ketone metabolism. Glucose enters the cell via a glucose transporter (Glut-1) and is converted to pyruvate through glycolysis in the cytoplasm. Pyruvate then enters the mitochondria, where it's converted to Acetyl-CoA, initiating the Krebs cycle (also known as the citric acid cycle). This cycle produces NADH and ATP, which are essential for cellular energy. When glucose is limited, ketone bodies enter the cell via monocarboxylate transporters (MCTs) and are converted to Acetyl-CoA, feeding into the Krebs cycle to produce energy.
  • Integration of metabolic pathways: The diagram depicts the interconnectedness of glucose and ketone metabolism in a normal brain cell. The figure shows that both glucose and ketone bodies are metabolized to Acetyl-CoA, which enters the Krebs cycle. The Krebs cycle is a series of chemical reactions that extract energy from Acetyl-CoA and generate molecules like NADH and ATP, which the cell uses for fuel.
  • Role of transporters: The figure highlights the role of specific transporters, Glut-1 for glucose and MCTs for ketone bodies, in facilitating the entry of these substrates into the cell. These transporters are crucial for cellular metabolism because they regulate the availability of energy substrates inside the cell.
Scientific Validity
  • Accuracy of metabolic representation: The diagram accurately represents the core biochemical pathways of glucose and ketone metabolism in a normal brain cell. However, it simplifies the complexity of these processes by omitting regulatory enzymes and intermediate steps, which could be misleading for experts seeking detailed mechanistic insights.
  • Completeness of metabolic pathways: The schematic representation does not include all possible metabolic fates of pyruvate or Acetyl-CoA, such as lipid synthesis or amino acid metabolism, which are also relevant in brain cells. This omission could oversimplify the metabolic capabilities of normal brain cells.
  • Inclusion of regulatory mechanisms: The figure does not explicitly address the regulation of glucose and ketone metabolism, such as hormonal control or allosteric regulation of key enzymes. Including these regulatory aspects would provide a more complete picture of metabolic control in normal brain cells.
Communication
  • Overall clarity and visual representation: The diagram effectively uses visual cues to represent metabolic pathways, making it easier to understand the complex processes involved. The use of arrows and labels is clear, but could benefit from more specific annotations to highlight key regulatory steps or enzyme involvement.
  • Caption completeness: The caption provides a basic description of the figure's content, but could be expanded to include the specific context within the study (i.e., how this normal cell metabolism contrasts with that of a cancer cell) to improve its immediate relevance to the reader.
  • Accessibility for non-experts: For readers unfamiliar with metabolic pathways, a brief glossary or more detailed introduction to the key molecules and processes (e.g., glycolysis, Krebs cycle) would enhance understanding.
FIGURE 1 (B) Ketogenic diet impact in normal brain cells.
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FIGURE 1 (B) Ketogenic diet impact in normal brain cells.
First Reference in Text
Glucose and ketone metabolism in normal and cancer cells is illustrated in Figures 1A, B, 2A, B.
Description
  • Overview of ketogenic diet impact: Figure 1B illustrates how a ketogenic diet affects metabolism in a normal brain cell. A ketogenic diet is a diet very low in carbohydrates, moderate in protein, and high in fats. When carbohydrates are restricted, the body produces ketone bodies from fat, which serve as an alternative fuel source. In this diagram, the ketogenic diet is shown to inhibit glucose uptake by the brain cell, represented by a crossed-out glucose transporter (Glut-1).
  • Shift in substrate utilization: The figure shows that ketone bodies enter the cell via monocarboxylate transporters (MCTs). Once inside, they're converted to Acetyl-CoA, which then enters the Krebs cycle to produce energy. The ketogenic diet forces the brain cell to rely more heavily on ketone bodies for fuel instead of glucose.
  • Metabolic consequences: The diagram highlights the reduced reliance on glucose and increased utilization of ketone bodies in normal brain cells during a ketogenic diet. This metabolic shift is thought to have therapeutic benefits in certain neurological conditions.
Scientific Validity
  • Accuracy of metabolic representation: The diagram accurately represents the core concept of reduced glucose utilization and increased ketone body utilization in normal brain cells under a ketogenic diet. However, it simplifies the complex regulatory mechanisms that govern substrate selection and metabolic flux.
  • Completeness of adaptive mechanisms: The figure does not address the potential adaptive mechanisms that brain cells might employ to compensate for reduced glucose availability, such as increased expression of ketone body transporters or altered enzyme activity. This omission could limit the figure's scientific rigor.
  • Inclusion of energy status: The figure does not explicitly show the effects on ATP production or energy status within the cell, which are key outcomes of the metabolic shift. Including this information would strengthen the figure's scientific validity.
Communication
  • Visual representation of metabolic shift: The diagram effectively illustrates the shift in substrate utilization in normal brain cells under a ketogenic diet. The visual representation of reduced glucose entry and increased ketone body entry is clear. However, the figure could benefit from a more explicit depiction of the relative concentrations or flux rates of these substrates to better convey the quantitative impact of the diet.
  • Contextual information in caption: The caption provides context for the figure, but it could be enhanced by mentioning the intended benefit or consequence of this metabolic shift in normal brain cells, such as neuroprotection or energy efficiency.
  • Accessibility for non-experts: While the diagram is simplified, it assumes a certain level of familiarity with metabolic pathways. Providing a brief explanation of the rationale behind the ketogenic diet's impact on glucose and ketone body utilization would improve accessibility for readers without a strong background in metabolism.
FIGURE 2 (A) Simplified schema of glucose and fat metabolism in a cancer cells.
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FIGURE 2 (A) Simplified schema of glucose and fat metabolism in a cancer cells.
First Reference in Text
Glucose and ketone metabolism in normal and cancer cells is illustrated in Figures 1A, B, 2A, B.
Description
  • Overview of cancer cell metabolism: Figure 2A depicts the metabolic processes within a cancer cell, emphasizing the Warburg effect, which is the preference for glycolysis (the breakdown of glucose) over oxidative phosphorylation (the use of oxygen to generate energy in the mitochondria) even when oxygen is available. Glucose enters the cell and is converted to pyruvate, but instead of primarily entering the mitochondria, it's converted to lactate via anaerobic glycolysis.
  • Mitochondrial dysfunction: The figure indicates that the mitochondria in cancer cells are dysfunctional. This is represented by dashed lines around the Krebs cycle and reduced ATP production, implying that oxidative phosphorylation is impaired. The cancer cell relies heavily on glycolysis for its energy needs.
  • Lactate production and tumor microenvironment: The diagram shows the production of lactate, which is exported from the cell. Lactate production contributes to an acidic environment around the tumor, which can promote cancer progression and metastasis. Acidosis, lactate and MCTs are highlighted.
Scientific Validity
  • Accuracy of metabolic representation: The diagram accurately represents the core features of cancer cell metabolism, including increased glycolysis and mitochondrial dysfunction. However, it is a simplified representation and does not capture the full complexity of metabolic heterogeneity within tumors.
  • Completeness of metabolic pathways: The figure does not include other important metabolic pathways that are often dysregulated in cancer cells, such as glutamine metabolism or fatty acid synthesis. Including these pathways would provide a more complete picture of cancer cell metabolism.
  • Inclusion of regulatory mechanisms: The figure does not explicitly address the genetic and epigenetic factors that contribute to the metabolic rewiring of cancer cells. Mentioning key oncogenes or tumor suppressor genes that regulate metabolism would enhance the figure's scientific validity.
Communication
  • Clarity of visual representation: The diagram clearly illustrates the metabolic differences in cancer cells compared to normal cells, specifically highlighting the reliance on glycolysis and reduced mitochondrial function. The use of simplified schematics effectively conveys the overall metabolic phenotype.
  • Caption completeness: The caption provides a basic description, but could be enhanced by explicitly stating the Warburg effect and how it is represented in the figure. Mentioning the therapeutic implications (i.e., targeting glycolysis) would also improve the caption's impact.
  • Accessibility for non-experts: For readers unfamiliar with cancer metabolism, a brief explanation of why cancer cells favor glycolysis even in the presence of oxygen (Warburg effect) would improve understanding.
FIGURE 2 (B) Ketogenic diet impact in cancer cells.
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FIGURE 2 (B) Ketogenic diet impact in cancer cells.
First Reference in Text
Glucose and ketone metabolism in normal and cancer cells is illustrated in Figures 1A, B, 2A, B.
Description
  • Overview of ketogenic diet impact: Figure 2B illustrates the effects of a ketogenic diet on cancer cell metabolism. The diagram shows a crossed-out glucose transporter (Glut-1), indicating that the ketogenic diet reduces glucose uptake into the cancer cell. This is because the ketogenic diet aims to lower blood glucose levels, thus depriving cancer cells of their preferred fuel source.
  • Impaired ketone body oxidation: The diagram indicates that even though ketone bodies are available, the cancer cell's ability to oxidize them efficiently is impaired due to mitochondrial abnormalities. This is represented by the dashed lines around the Krebs cycle, implying that the cancer cell cannot effectively use ketone bodies for energy production.
  • Therapeutic consequences: The figure highlights that the combination of reduced glucose uptake and impaired ketone body oxidation leads to reduced proliferation rates in cancer cells. This is the intended therapeutic effect of the ketogenic diet.
Scientific Validity
  • Accuracy of metabolic representation: The diagram accurately represents the intended metabolic effects of a ketogenic diet on cancer cells, including reduced glucose availability and impaired ketone body oxidation. However, it is a simplified representation and does not capture the full complexity of metabolic adaptations that cancer cells can undergo.
  • Completeness of metabolic pathways: The figure does not address the potential for cancer cells to upregulate other metabolic pathways, such as glutamine metabolism or fatty acid oxidation, to compensate for the reduced glucose availability. Including these alternative pathways would provide a more complete picture of cancer cell metabolism.
  • Inclusion of microenvironmental factors: The figure does not explicitly address the role of the tumor microenvironment or systemic factors that can influence cancer cell metabolism. Including these factors would enhance the figure's scientific validity.
Communication
  • Clarity of visual representation: The diagram effectively illustrates the intended impact of a ketogenic diet on cancer cells, specifically highlighting the reduction in glucose availability and the potential for reduced proliferation rates. The use of crossed-out arrows effectively conveys the inhibition of glucose uptake.
  • Caption completeness: The caption could be enhanced by explicitly mentioning the therapeutic rationale, which is to exploit the metabolic inflexibility of cancer cells and their dependence on glucose. Also, stating the potential limitations (i.e., cancer cells may still use ketone bodies) would improve the caption's completeness.
  • Accessibility for non-experts: For readers unfamiliar with cancer metabolism, a brief explanation of why limiting glucose might be detrimental to cancer cell growth would improve understanding. It could also benefit from acknowledging the potential for metabolic adaptation.

Materials and methods

Key Aspects

Strengths

Suggestions for Improvement

Non-Text Elements

TABLE 1 Characteristics of all patients who participated in the study.
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TABLE 1 Characteristics of all patients who participated in the study.
First Reference in Text
Grades 2 and 3 are intermediary forms (32) (Table 1).
Description
  • Overview of patient characteristics: Table 1 presents the characteristics of all 18 patients who participated in the study. The table includes the following information for each patient: patient identifier (P), gender (G), age (A), date of diagnosis (DD), date of surgery and type of operation (DS-TOO), chemotherapy and radiation therapy administered before the ketogenic diet (Chemo + Rad prior KD administration), and molecular biology (MB).
  • Patient demographics and surgical information: The table shows a mix of male (M) and female (F) patients, with ages ranging from 34 to 75 years. The 'DS-TOO' column indicates whether the patient underwent total resection or subtotal resection/stereotactic biopsy. Total resection refers to complete removal of the tumor, while subtotal resection means that part of the tumor was left.
  • Treatment and molecular biology information: The 'Chemo + Rad prior KD administration' column lists the specific chemotherapeutic agents (Temozolamide) and the use of radiation therapy, specifically mentioning 30 cycles of radiation. The 'MB' column indicates the IDH1 status of the tumor, with results showing either negative (-), positive (+), or IDH 1-2.
Scientific Validity
  • Relevance of included variables: The table provides relevant descriptive information about the patient cohort, which is essential for assessing the study's generalizability. The inclusion of molecular biology data (IDH1 status) is important for characterizing the tumor subtypes.
  • Completeness of clinical data: The table is missing key clinical data that could influence the outcomes, such as Karnofsky Performance Status (KPS) scores at baseline, ECOG scores, extent of resection, and details of concurrent treatments. Adding these variables would strengthen the table's scientific value.
  • Transparency of data collection: The table does not indicate the source of the patient data or the methods used to collect it. Clearly stating the data collection procedures would improve the table's transparency and scientific rigor.
Communication
  • Overall organization and presentation: The table is generally well-organized, providing essential information about the study participants. However, the table could benefit from including summary statistics (e.g., mean ± SD for age) to allow for easier comparison between groups.
  • Clarity of abbreviations: The use of abbreviations is generally defined, but a glossary of abbreviations within the table or in the caption would ensure clarity for all readers.
  • Relevance to study objectives: The table effectively presents the data to support the study's methods. However, consider adding a column indicating whether each patient adhered to the ketogenic diet and for how long, as this is a critical variable in the study.

Results

Key Aspects

Strengths

Suggestions for Improvement

Non-Text Elements

TABLE 2 Example of ketogenic diet 2,150 Kcal 2:1 ratio.
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TABLE 2 Example of ketogenic diet 2,150 Kcal 2:1 ratio.
First Reference in Text
An example of the diet applied is shown in Table 2.
Description
  • Overview of the ketogenic diet example: Table 2 provides an example of a ketogenic diet with a total daily calorie intake of 2,150 Kcal and a 2:1 ketogenic ratio. The ketogenic ratio refers to the ratio of fat to combined protein and carbohydrates in the diet. The table lists specific food items and their quantities for morning, snack, lunch, snack, and dinner meals.
  • Specific food items for main meals: The morning meal consists of 17g tuna in oil and 8g olive oil. The lunch meal includes 93g sardines and 41g olive oil, while dinner consists of 117g raw green salad, 93g salmon, and 41g olive oil.
  • Specific food items for snacks: The snack options include items like 20g feta cheese, 60g keto-focaccia, 1 egg fortified with w-3 fatty acids, and 15g avocado. The table provides a 'Daily menu plan' indicating the distribution of food items across the day.
Scientific Validity
  • Lack of design criteria: The table provides an example of a ketogenic diet, but it lacks information on the specific criteria used to design the diet (e.g., target blood ketone levels, individual patient needs). Including this information would improve the table's scientific rigor.
  • Missing source of food composition data: The table does not specify the source of the food composition data used to calculate the macronutrient content of the diet. Providing this information would enhance the table's transparency and scientific validity.
  • Nutritional completeness: The table presents a single example, but it doesn't indicate whether this diet is nutritionally complete or if it was supplemented with vitamins or minerals. Including this information would improve the table's scientific validity.
Communication
  • Completeness of macronutrient information: The table provides a useful example of a ketogenic diet, but it lacks information on the macronutrient breakdown (grams of fat, protein, carbohydrates) for each meal. Including this information would allow readers to assess the diet's composition and adherence to the 2:1 ratio more effectively.
  • Inclusion of meal timing: The table presents a daily menu plan, but it does not specify the timing of the meals or snacks. Including this information would provide a more complete picture of the dietary regimen.
  • Representativeness of the example: The table provides a specific example, but it doesn't indicate whether this was a standard diet or if it was individualized based on patient preferences or tolerances. Clarifying this aspect would enhance the table's value.
FIGURE 3 Patient 1: (A) Pre-operative brain MRI (T2/FLAIR) (B) Pre-operative...
Full Caption

FIGURE 3 Patient 1: (A) Pre-operative brain MRI (T2/FLAIR) (B) Pre-operative brain MRI (T1 with contrast) (C) 38-month follow-up brain MRI (T1 with contrast) (D) 80-month follow-up brain MRI (T1 with contrast).

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