Low-carbohydrate Ketogenic Diet Research Articles

Abstract PO3-02-03: Ketogenic diet and letrozole to inhibit PI3K signaling in ER+ breast cancer

Abstract Obesity is associated with an increased risk of breast cancer recurrence, similar in magnitude to the reduction in risk seen with the use of adjuvant chemotherapy. However, whether and how obesity causes that increased risk of recurrence remains unknown. Plausible mechanisms include obesity-mediated increases in estrogen signaling, inflammatory conditions resulting from obesity, or effects on insulin or other growth factor signaling pathways resulting from the insulin-resistant state that often accompanies obesity. While phosphatidyl inositol 3-kinase (PI3K) signaling is the normal, biological effector of insulin signaling, abnormal activation of PI3K is of particular concern in breast cancer, where it is associated with resistance to endocrine therapies and HER2-targeted therapies. We hypothesize that at least part of the adverse outcome associated with obesity results from aberrant activation of PI3K signaling in tumors. This may confer resistance to established therapies, or directly stimulate tumor growth (particularly in tumors with existing PI3K pathway mutations), or both. We tested a dietary intervention designed to alter insulin resistance pathophysiology coupled with endocrine therapy in the well-established neoadjuvant treatment paradigm in breast cancer. This will allow us to study the effects of the dietary intervention directly on tumor biology. The primary objective of this neoadjuvant study was to assess feasibility and tolerability of 2 weeks of a very low-carbohydrate ketogenic diet in combination with letrozole for patients with early stage operable ER+ disease. Up to 36 patients will be enrolled for this pilot and feasibility study (24 in the treatment group and 12 controls). Baseline metabolic parameters will be measured and the treatment group will begin a dietitian-supervised 2-week diet to induce a ketogenic state, along with letrozole 2.5 mg daily. The control group will receive only letrozole. At the end of 2 weeks, patients will proceed with surgical treatment of their breast cancer. We will report the primary outcome measure of feasibility, assessed by determining 1) the proportion of patients in the diet group achieving ketosis, 2) adherence to the diet and 3) participant-reported measures of stress, fatigue, and emotional health. For both groups, cell proliferation will be measured in a tumor biopsy obtained from the surgical specimen and compared with the pre-treatment diagnostic biopsy. Correlative studies will evaluate tumor markers of insulin/PI3K signaling before and after the intervention and between diet and control. Citation Format: Brent Rexer, Vandana Abramson, Sara Nunnery, Sonya Reid, Laura Kennedy, Melinda Sanders, Jessica Bennett, Paula Gonzalez-Ericsson, Violeta Sanchez. Ketogenic diet and letrozole to inhibit PI3K signaling in ER+ breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-02-03.

A ketogenic diet enhances fluconazole efficacy in murine models of systemic fungal infection.

Invasive fungal infections are a significant public health concern, with mortality rates ranging from 20% to 85% despite current treatments. Therefore, we examined whether a ketogenic diet could serve as a successful treatment intervention in murine models of Cryptococcus neoformans and Candida albicans infection in combination with fluconazole-a low-cost, readily available antifungal therapy. The ketogenic diet is a high-fat, low-carbohydrate diet that promotes fatty acid oxidation as an alternative to glycolysis through the production of ketone bodies. In this series of experiments, mice fed a ketogenic diet prior to infection with C. neoformans and treated with fluconazole had a significant decrease in fungal burden in both the brain (mean 2.66 ± 0.289 log10 reduction) and lung (mean 1.72 ± 0.399 log10 reduction) compared to fluconazole treatment on a conventional diet. During C. albicans infection, kidney fungal burden of mice in the keto-fluconazole combination group was significantly decreased compared to fluconazole alone (2.37 ± 0.770 log10-reduction). Along with higher concentrations of fluconazole in the plasma and brain tissue, fluconazole efficacy was maximized at a significantly lower concentration on a keto diet compared to a conventional diet, indicating a dramatic effect on fluconazole pharmacodynamics. Our findings indicate that a ketogenic diet potentiates the effect of fluconazole at multiple body sites during both C. neoformans and C. albicans infection and could have practical and promising treatment implications.IMPORTANCEInvasive fungal infections cause over 2.5 million deaths per year around the world. Treatments for fungal infections are limited, and there is a significant need to develop strategies to enhance antifungal efficacy, combat antifungal resistance, and mitigate treatment side effects. We determined that a high-fat, low-carbohydrate ketogenic diet significantly potentiated the therapeutic effect of fluconazole, which resulted in a substantial decrease in tissue fungal burden of both C. neoformans and C. albicans in experimental animal models. We believe this work is the first of its kind to demonstrate that diet can dramatically influence the treatment of fungal infections. These results highlight a novel strategy of antifungal drug enhancement and emphasize the need for future investigation into dietary effects on antifungal drug activity.

The Significant Impact of High-Fat, Low-Carbohydrate Ketogenic Diet on Serum Lipid Profile and Atherosclerotic Cardiovascular Disease Risk in Overweight and Obese Adults.

Background and objectives Overweight and obesity are becoming more commonplace globally. The ketogenic diet (KD), also known as the high-fat, low-carbohydrate diet, has become increasingly popular in recent years as a means to lose weight quickly. This present study aims to examine the clinical effects of ketogenic diets in individuals who are obese or overweight by evaluating or assessing variations in metabolic parameters associated with lipid control, the risk of atherosclerotic cardiovascular disease, and other kidney risk indicators. Methods and subjects This observational case-control research involved 250 individuals in total and was conducted from May 2023 to January 2024. Of these, 158 were on a ketogenic diet, and 92 adults not following any type of diet were chosen to serve as controls. The biochemistry parameters of the kidney function test and lipid profile were measured for the two comparing groups. Data were analyzed for statistical significance using the Student t-test, Mann-Whitney U test, and one-way analysis of variance (ANOVA), followed by a post hoc test (least significant difference (LSD)). Chi-square tests were employed in the analysis to compare proportions. Results Out of 250 participants, there was a 20-80 age range, with their median age being 40 years old. The two comparing groups' lipid profiles were very different from one another; the cardiovascular risk (triglyceride (TG)/high-density lipoprotein (HDL)), total cholesterol, low-density lipoprotein (LDL), and triglyceride levels were all greater in the KD group when compared to the non-KD group. The mean LDL cholesterol (LDL-C) of the normal-weight participants was 56 mg/dL (p=0.079). Thereafter, it experienced a significant rise to 97.58 mg/dL and 108.2 mg/dL in thoseindividuals who were overweight and obese, respectively (p<0.020). Conclusions As obesity rates in the populace keep rising, dietary fads such as the ketogenic diet are gaining traction. Although they could help with weight loss, this study had a notable observation of severe hypercholesterolemia and increased risk of atherosclerotic cardiovascular disease among the ketogenic diet participants. Additional research is necessary to ascertain if a ketogenic diet can be sustained over the long term and how it affects endpoints that are more clinically significant, such as morbidity and mortality due to obesity.

Effects of ketogenic diet on weight loss parameters among obese or overweight patients with polycystic ovary syndrome: a systematic review and meta-analysis of randomized controlled trails.

To evaluate how effective a low carbohydrate ketogenic diet (KD) is for changing key physical measurements such as weight, waist circumference (WC), body mass index (BMI), and fat mass (FM) in women with polycystic ovary syndrome (PCOS) who were obese or overweight. Several online databases, including PubMed, Scopus, EMBASE, Cochrane Library, and Web of Science (WOS), were searched systematically to find relevant randomized controlled trials (RCTs) up until June 2023. The Q-test and I2 statistics were used to assess the level of heterogeneity among the included studies. The data were then combined using either a fixed or random effects model and presented as a weighted mean difference (WMD) along with a 95% confidence interval (CI). Of the 682 citations, 11 RCTs were included. The pooled results showed a significant decrease in the WMD of weight levels [WMD = -9.13 kg; 95% CI, -11.88, -6.39, P < 0.001; I2 = 87.23%] following KD. Moreover, KD significantly reduced BMI levels [WMD = -2.93 kg/m2; 95% CI, -3.65, -2.21, P < 0.001; I2 = 78.81%] compared to the controls. Patients with PCOS received KD demonstrated significant decrease in WC [WMD = -7.62 cm; 95% CI, -10.73, -4.50, P < 0.001; I2 = 89.17%] and FM [WMD = -5.32 kg; 95% CI, -7.29, -3.36, P < 0.001; I2 = 83.97%]. KD was associated with lower weight loss (WL) parameters, including weight, BMI, WC, and FM, in obese or overweight women with PCOS, highlighting the significance of physicians and nurses in taking care of the nutritional needs of overweight/obese patients with PCOS.

Dietary and Metabolic Approaches for Treating Autism Spectrum Disorders, Affective Disorders and Cognitive Impairment Comorbid with Epilepsy: A Review of Clinical and Preclinical Evidence.

Epilepsy often occurs with other neurological disorders, such as autism, affective disorders, and cognitive impairment. Research indicates that many neurological disorders share a common pathophysiology of dysfunctional energy metabolism, neuroinflammation, oxidative stress, and gut dysbiosis. The past decade has witnessed a growing interest in the use of metabolic therapies for these disorders with or without the context of epilepsy. Over one hundred years ago, the high-fat, low-carbohydrate ketogenic diet (KD) was formulated as a treatment for epilepsy. For those who cannot tolerate the KD, other diets have been developed to provide similar seizure control, presumably through similar mechanisms. These include, but are not limited to, the medium-chain triglyceride diet, low glycemic index diet, and calorie restriction. In addition, dietary supplementation with ketone bodies, polyunsaturated fatty acids, or triheptanoin may also be beneficial. The proposed mechanisms through which these diets and supplements work to reduce neuronal hyperexcitability involve normalization of aberrant energy metabolism, dampening of inflammation, promotion of endogenous antioxidants, and reduction of gut dysbiosis. This raises the possibility that these dietary and metabolic therapies may not only exert anti-seizure effects, but also reduce comorbid disorders in people with epilepsy. Here, we explore this possibility and review the clinical and preclinical evidence where available.

Abstract C052: Ketogenic diet enhanced nutrient metabolic pathways but did not inhibit tumor growth in an obesity-associated PDAC mouse model

Abstract Background: Pancreatic ductal adenocarcinoma (PDAC) has a dismal 5-year survival rate due to ineffective treatments. Obesity is a recognized risk factor for PDAC. Thus, developing effective weight management strategies is essential to decrease obesity, and potentially mitigate PDAC risk. The high-fat, low-carbohydrate ketogenic diet (KD) promotes weight loss and is a promising therapeutic strategy in some cancer preclinical models by altering tumor metabolism. Purpose: The KD will disrupt cancer metabolism, promote weight loss, and delay tumor growth in obesity-associated PDAC. Methods: C57BL/6 mice were fed an obesogenic high-fat diet (HFD) for 15 weeks to induce obesity, after which were randomized to a control diet (CD), a KD, or continued in the HFD for 7 weeks. After, mice were orthotopically injected with mouse KRas G12D/Trp53−/−/PDX-1-CRE (mKPC) cells containing the firefly luciferase gene. Tumor growth was monitored using luminescence through an In Vivo Imaging System. Body weight, glucose tolerance tests, and ketone measurements were performed before, during, and at the study end. Tumors metabolomics were analyzed by Liquid Chromatography Mass Spectrometry. Results: Mice gained weight after 15 weeks of an obesogenic diet. Mice that were switched to a KD or CD lost weight compared to mice that remained on the HFD following diet intervention. Mice fed a KD maintained increased ketone concentrations and increased glucose tolerance after tumors. However, none of the dietary interventions decreased tumor growth. Tumors in mice fed a KD showed significant enrichment in metabolic processes, such as, vitamin B6 and vitamin B5 metabolism, the citrate cycle, and arginine biosynthesis compared to mice that remained on a HFD. Conclusions: Although the KD induced weight loss and altered tumor metabolism, it was insufficient to decrease tumor growth in an obesogenic PDAC mouse model. Our data identified vitamin B6 and vitamin B5 metabolism, the citrate cycle, and arginine biosynthesis as important compensatory metabolic processes induced by the KD. Understanding the availability and functions of these metabolic processes could identify mechanisms of diet interventions for obesity-associated PDAC to decrease obesity, and potentially mitigate PDAC growth. Citation Format: Ericka Velez-Bonet, Kristyn Gumpper-Fedus, Fouad Choueiry, Zhu Jiangjiang, Zobeida Cruz-Monserrate. Ketogenic diet enhanced nutrient metabolic pathways but did not inhibit tumor growth in an obesity-associated PDAC mouse model [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr C052.

Ketogenic diet for epilepsy and obesity: Is it the same?

The term “ketogenic diet” (KD) is used for a wide variety of diets with diverse indications ranging from obesity to neurological diseases, as if it was the same diet. This terminology is confusing for patients and the medical and scientific community. The term “ketogenic” diet implies a dietary regimen characterized by increased levels of circulating ketone bodies that should be measured in blood (beta-hydroxybutyrate), urine (acetoacetate) or breath (acetone) to verify the “ketogenic metabolic condition”. Our viewpoint highlights that KDs used for epilepsy and obesity are not the same; the protocols aimed at weight loss characterized by low-fat, low-CHO and moderate/high protein content are not ketogenic by themselves but may become mildly ketogenic when high calorie restriction is applied. In contrast, there are standardized protocols for neurological diseases treatment for which ketosis has been established to be part of the mechanism of action. Therefore, in our opinion, the term ketogenic dietary therapy (KDT) should be reserved to the protocols considered for epilepsy and other neurological diseases, as suggested by the International Study Group in 2018. We propose to adjust the abbreviations in VLCHKD for Very Low CarboHydrate Ketogenic Diet and VLEKD for Very Low Energy Ketogenic Diet, to clarify the differences in dietary composition. We recommend that investigators describe the researchers describing efficacy or side effects of KDs, to clearly specify the dietary protocol used with its unique acronym and level of ketosis, when ketosis is considered as a component of the diet's mechanism of action.

Ketogenic strategies for Alzheimer’s disease and other memory impairments: History, rationale, and 288 caregiver case reports

Glucose hypometabolism predates Alzheimer’s disease symptoms by at least one to two decades. Ketones are an alternative fuel to glucose and are taken up normally in affected regions of the Alzheimer’s brain and could address certain pathologies that are common in the aging brain and exaggerated in Alzheimer’s disease including insulin resistance, a brain-energy deficit, mitochondrial dysfunction, oxidative stress, and neuroinflammation. Ketones have also been shown to reduce formation of beta-amyloid plaques and neurofibrillary tangles in animal models. Experts have estimated that at least 30 percent of Alzheimer’s and other dementias could be avoided by adopting a healthy diet, increasing physical activity, and correcting other modifiable lifestyle risk factors. Mild to moderate ketosis can be achieved through consumption of a healthy whole food low-carbohydrate ketogenic diet, ketogenic oils containing medium-chain triglycerides, or exogenous ketone supplements as well as intermittent or overnight fasting, and moderately vigorous aerobic exercise. An analysis was performed of 288 anecdotal reports about people with Alzheimer’s, other dementias, Parkinson’s disease with dementia, mild cognitive impairment, and other diagnosed or subjective memory impairments consuming coconut oil and/or medium-chain triglyceride oil. Improvement was reported by 89.2 percent, no improvement by 7.3 percent, and no improvement but stabilization for at least 3 months by 2.4 percent. One or more improvements were reported in the areas of memory/cognition (65.3%), social/behavior/ mood/personality (32.6%), speech/language/conversation (33%), resumption of self-care/other activities (24.7%), physical symptoms (18.4%), sleep (3.5%), appetite (2.4%), vision (1.4%), and improvement that was otherwise unspecified (8%). Certain fatty acids found in medium-chain triglyceride oil and coconut oil are ketogenic but also have other important biological effects which, along with polyphenols and other bioactive substances in virgin coconut oil, could explain these results. Adopting a personalized ketogenic lifestyle plan using one or more ketogenic strategies could address certain pathological processes that occur in the aging brain while potentially improving symptoms in people with Alzheimer’s disease. In addition, this approach could possibly prevent or delay the onset of cognitive impairment during aging, though larger long-term studies would be needed to confirm this.

Nutritional Intervention in Cushing's Disease: The Ketogenic Diet's Effects on Metabolic Comorbidities and Adrenal Steroids.

a very low-calorie ketogenic diet (VLCKD) is associated with improvement of metabolic and cardiovascular disorders. We aimed to evaluate the effects of a VLCKD in patients with Cushing's disease (CD) as adjunctive therapy to treatment for the primary disease. we evaluated clinical, hormonal and metabolic parameters in 15 patients with CD and 15 controls at baseline after 1 week and 3 weeks of VLCKD and, further, after 2 weeks of a low-carbohydrate ketogenic diet (LCKD). after 5 weeks of diet, a significant decrease in BMI (p = 0.002), waist circumference (WC) (p = 0.024), systolic blood pressure (p = 0.015), diastolic blood pressure (p = 0.005), ACTH (p = 0.026), cortisone (p = 0.025), total cholesterol (p = 0.006), LDL cholesterol (p = 0.017), triglycerides (p = 0.016) and alkaline phosphatase (p = 0.008) and a significant increase in HDL cholesterol (p = 0.017), vitamin D (p = 0.015) and oral disposition index (oDI) (p = 0.004) was observed in the CD patients. A significant decrease in BMI (p = 0.003), WC (p = 0.002), systolic blood pressure (p = 0.025), diastolic (p = 0.007) blood pressure and total cholesterol (p = 0.026) and an increase in HDL cholesterol (p = 0.001) and oDI (p < 0.001) was observed in controls. the current study confirms that a ketogenic diet is effective in improving metabolic disorders in CD and shows that a nutritional approach may be combined with conventional CD therapy in order to improve metabolic and cardiovascular comorbidities.

Glucose restriction induces AMPK-SIRT1-mediated circadian clock gene Per expression and delays NSCLC progression

The rhythmic expression of the circadian clock is intimately linked to the health status of the body. Disturbed circadian clock rhythms might lead to a wide range of metabolic diseases and even cancers. Our previous study showed that glucose restriction was able to inhibit non-small cell lung cancer (NSCLC). In the current study, we found that glucose restriction enhanced apoptosis and cell growth delay in NSCLC cells. In addition, we used GEPIA database analysis to derive different effects of each circadian clock gene on lung cancer tissue. Among these circadian clock genes, Per (Period) is lowly expressed in cancer tissues and highly expressed in normal tissues. Moreover, the higher expression of Per in cancer patients has a better prognostic significance. Furthermore, we revealed that glucose restriction induced the expression of the circadian clock gene Per in NSCLC cells by upregulating SIRT1 (Sirtuin1) via activation of the energy response factor AMPK (AMP-activated protein kinase). Changes in Per expression following upregulation or downregulation of AMPK were consistent with AMPK expression. Additionally, a low-carbohydrate ketogenic diet significantly delayed tumor progression in a xenograft tumor model of severe combined immunodeficiency (SCID) mice. Meanwhile, the ketogenic diet increased the expression of AMPK, SIRT1 and Per in vivo. Besides, the ketogenic diet was found to restore the normal rhythmic level of Per by Zeitgeber Time (ZT) experiments. Taken these together, these results indicated a novel mechanism that glucose restriction induces AMPK-SIRT1 mediated circadian clock gene Per expression and delays NSCLC progression, which provided more evidence for glucose restriction as an adjuvant clinical therapeutic strategy in NSCLC.

Ketogenic Diet Affects Sleep Architecture in C57BL/6J Wild Type and Fragile X Mice.

Nearly half of children with fragile X syndrome experience sleep problems including trouble falling asleep and frequent nighttime awakenings. The goals here were to assess sleep-wake cycles in mice in response to Fmr1 genotype and a dietary intervention that reduces hyperactivity. Electroencephalography (EEG) results were compared with published rest-activity patterns to determine if actigraphy is a viable surrogate for sleep EEG. Specifically, sleep-wake patterns in adult wild type and Fmr1KO littermate mice were recorded after EEG electrode implantation and the recordings manually scored for vigilance states. The data indicated that Fmr1KO mice exhibited sleep-wake patterns similar to wild type littermates when maintained on a control purified ingredient diet. Treatment with a high-fat, low-carbohydrate ketogenic diet increased the percentage of non-rapid eye movement (NREM) sleep in both wild type and Fmr1KO mice during the dark cycle, which corresponded to decreased activity levels. Treatment with a ketogenic diet flattened diurnal sleep periodicity in both wild type and Fmr1KO mice. Differences in several sleep microstructure outcomes (number and length of sleep and wake bouts) supported the altered sleep states in response to a ketogenic diet and were correlated with altered rest-activity cycles. While actigraphy may be a less expensive, reduced labor surrogate for sleep EEG during the dark cycle, daytime resting in mice did not correlate with EEG sleep states.

What We Have Learned About Combining a Ketogenic Diet and Chemoimmunotherapy: a Case Report and Review of Literature.

A high-fat, moderate-protein, low-carbohydrate ketogenic diet has been reported in the literature as a treatment option for patients with cancer. A 69-year-old veteran was initially diagnosed with stage III colorectal cancer and progressed to having liver, pancreatic, and omental lymph node involvement despite completing adjuvant FOLFOX (fluorouracil, leucovorin calcium, and oxaliplatin) after surgery. The patient was treated with FOLFIRI (fluorouracil, leucovorin calcium, and irinotecan hydrochloride) and bevacizumab, followed by encorafenib and cetuximab on progression. Subsequently, he received pembrolizumab but continued to progress. The patient was later placed on trifluridine/tipiracil and bevacizumab concurrent with a ketogenic diet. Positron emission tomography and carcinoembryonic antigen levels indicated disease stabilization for 10 months. On progression, the patient was transitioned to ipilumimab and nivolumab and continued to adhere to the ketogenic diet. The patient's disease has continued to remain stable for the past 1 year. His degree of ketosis was determined using the glucose ketone index. The patient continues to have a good quality of life during concurrent ketogenic diet and therapy. This case supports the tolerability of the ketogenic diet along with chemotherapy and immunotherapy and should be considered as an adjunct to standard cancer treatment. In this report, we reviewed the latest literature about cellular mechanism of the ketogenic diet and the efficacy and relationship with chemotherapy and immunotherapy. We are about to open a ketogenic diet protocol at the Veterans Affairs Central California Health Care System in Fresno.

Raf/MEK/ERK Signaling Pathway Is Involved in the Inhibition of Glioma Cell Proliferation and Invasion in the Ketogenic Microenvironment.

A high-fat, low-carbohydrate ketogenic diet has been used to treat malignant glioma, in which the Raf/MEK/ERK signaling pathway is overactivated. However, whether the Raf/MEK/ERK signaling pathway is involved in the therapeutic effect of ketone bodies remains unknown. In this study, we investigated the effects of a major ketone body, 3-hydroxybutyric acid (3-HBA), on the proliferation and metastasis of malignant glioblastoma cells and the underlying mechanism. Two human malignant glioblastoma cell lines (U87 and U251) were treated with different concentrations of 3-HBA with or without the Raf inhibitor PAF C-16 for 24 h. Cell proliferation, cell cycle, cell invasion, and phospholipase D1 (PLD1) activity were determined. Protein and gene expression levels of Raf/MEK/ERK signaling pathway members were examined. 3-HBA significantly decreased cell proliferation, invasion, and intracellular PLD1 activity in both U87 and U251 glioblastoma cell lines. 3-HBA treatment significantly increased the proportion of cells in the G1 phase and decreased the proportion of cells in S phase in U87 cells. In the U251 line, the proportion of treated cells in S phase was increased and proportion of cells in G2 was decreased. 3-HBA treatment also significantly decreased the protein expression levels of Raf, MEK, p-MEK, ERK, p-ERK, and PLD1 while increasing p53 expression; an effect that was similar to treatment with the Raf inhibitor. Co-treatment of 3-HBA with the Raf inhibitor further enhanced the effects of the 3-HBA in both cell lines. We confirmed that a ketogenic microenvironment can inhibit glioma cell proliferation and invasion by downregulating the expression of PLD1 through the Raf/MEK/ERK signaling pathway.

Ketogenic diet promotes tumor ferroptosis but induces relative corticosterone deficiency that accelerates cachexia

Glucose dependency of cancer cells can be targeted with a high-fat, low-carbohydrate ketogenic diet (KD). However, in IL-6-producing cancers, suppression of the hepatic ketogenic potential hinders the utilization of KD as energy for the organism. In IL-6-associated murine models of cancer cachexia, we describe delayed tumor growth but accelerated cachexia onset and shortened survival in mice fed KD. Mechanistically, this uncoupling is a consequence of the biochemical interaction of two NADPH-dependent pathways. Within the tumor, increased lipid peroxidation and, consequently, saturation of the glutathione (GSH) system lead to the ferroptotic death of cancer cells. Systemically, redox imbalance and NADPH depletion impair corticosterone biosynthesis. Administration of dexamethasone, a potent glucocorticoid, increases food intake, normalizes glucose levels and utilization of nutritional substrates, delays cachexia onset, and extends the survival of tumor-bearing mice fed KD while preserving reduced tumor growth. Our study emphasizes the need to investigate the effects of systemic interventions on both the tumor and the host to accurately assess therapeutic potential. These findings may be relevant to clinical research efforts that investigate nutritional interventions such as KD in patients with cancer.

Context-Dependent Effects of the Ketogenic Diet on Retinal Ganglion Cell Survival and Axonal Regeneration After Optic Nerve Injury.

Purpose: There is increasing interest in nonpharmacologic approaches to protect retinal ganglion cells (RGCs) after injury and enhance the efficacy of therapeutic molecules. Accumulating evidence demonstrates neuroprotection by the high-fat low-carbohydrate ketogenic diet (KD) in humans and animal models of neurologic diseases. However, no studies to date have examined whether the KD protects RGCs and promotes axonal regrowth after traumatic injury to the optic nerve (ON) or whether it increases efficacy of experimental proregenerative molecules. In this study, we investigated whether the KD promoted RGC survival and axonal regeneration after ON injury in the presence and absence of neuroprotective Wnt3a ligand. Methods: Adult mice were placed on a KD or control diet before ON crush injury and remained on the diet until the end of the experiment. Nutritional ketosis was confirmed by measuring serum beta-hydroxybutyrate levels. Mice were intravitreally injected with Wnt3a ligand or phosphate-buffered saline (PBS), and RGC survival, function, axonal regeneration, and inflammatory responses were measured. Results: Mice fed the KD showed increased RGC survival and reduced inflammatory cells in PBS-injected mice. Also, mice fed the KD had increased RGC functional responses but not increased RGC numbers in the presence of Wnt3a, indicating that the KD did not enhance the prosurvival effect of Wnt3a. The KD did not promote axonal regeneration in the presence or absence of Wnt3a. Conclusions: The KD has a complex protective effect after ON injury and cotreatment with Wnt3a. This work sets the foundation for studies identifying underlying molecular mechanisms.

Effects of very low carbohydrate ketogenic diets on skeletal health.

Very low carbohydrate ketogenic diet (KD) therapy has been associated with skeletal demineralization in children with drug-resistant epilepsy, but the cause of this association is unclear. Recently, interest in the KD has grown owing to its potential benefits for other illnesses including cancer, type 2 diabetes, obesity, and polycystic kidney disease. Summaries of the best available evidence regarding effects of a KD on skeletal health are lacking. Recent rodent studies found that a KD can harm the growing skeleton, which corroborates most but not all studies in pediatric patients. Proposed mechanisms include chronic metabolic acidosis and depressed osteoanabolic hormones. Relative to other weight-reducing diets, a weight-reducing KD for treatment of obesity and/or type 2 diabetes in adults has not been associated with adverse skeletal effects. By contrast, recent evidence suggests that adaptation to a eucaloric KD may impair bone remodeling in elite adult athletes. Discrepancies in the literature may relate to differences between study populations and in diet formulation. Attention to skeletal health is warranted when using KD therapy given the uncertainty in the literature and suggestive harms in certain populations. Future research should focus on potential mechanisms of injury.

Efficacy of low carbohydrate and ketogenic diets in treating mood and anxiety disorders: systematic review and implications for clinical practice.

There is mounting interest in the potential efficacy of low carbohydrate and very low carbohydrate ketogenic diets in various neurological and psychiatric disorders. To conduct a systematic review and narrative synthesis of low carbohydrate and ketogenic diets (LC/KD) in adults with mood and anxiety disorders. MEDLINE, Embase, PsycINFO and Cochrane databases were systematically searched for articles from inception to 6 September 2022. Studies that included adults with any mood or anxiety disorder treated with a low carbohydrate or ketogenic intervention, reporting effects on mood or anxiety symptoms were eligible for inclusion. PROSPERO registration CRD42019116367. The search yielded 1377 articles, of which 48 were assessed for full-text eligibility. Twelve heterogeneous studies (stated as ketogenic interventions, albeit with incomplete carbohydrate reporting and measurements of ketosis; diet duration: 2 weeks to 3 years; n = 389; age range 19 to 75 years) were included in the final analysis. This included nine case reports, two cohort studies and one observational study. Data quality was variable, with no high-quality evidence identified. Efficacy, adverse effects and discontinuation rates were not systematically reported. There was some evidence for efficacy of ketogenic diets in those with bipolar disorder, schizoaffective disorder and possibly unipolar depression/anxiety. Relapse after discontinuation of the diet was reported in some individuals. Although there is no high-quality evidence of LC/KD efficacy in mood or anxiety disorders, several uncontrolled studies suggest possible beneficial effects. Robust studies are now needed to demonstrate efficacy, to identify clinical groups who may benefit and whether a ketogenic diet (beyond low carbohydrate) is required and to characterise adverse effects and the risk of relapse after diet discontinuation.

Ketone bodies: A double-edged sword for mammalian life span.

Accumulating evidence suggests health benefits of ketone bodies, and especially for longevity. However, the precise role of endogenous ketogenesis in mammalian life span, and the safety and efficacy of the long-term exogenous supplementation of ketone bodies remain unclear. In the present study, we show that a deficiency in endogenous ketogenesis, induced by whole-body Hmgcs2 deletion, shortens life span in mice, and that this is prevented by daily ketone body supplementation using a diet containing 1,3-butanediol, a precursor of β-hydroxybutyrate. Furthermore, feeding the 1,3-butanediol-containing diet from early in life increases midlife mortality in normal mice, but in aged mice it extends life span and prevents the high mortality associated with atherosclerosis in ApoE-deficient mice. By contrast, an ad libitum low-carbohydrate ketogenic diet markedly increases mortality. In conclusion, endogenous ketogenesis affects mammalian survival, and ketone body supplementation may represent a double-edged sword with respect to survival, depending on the method of administration and health status.

Abstract 1162: Ketogenic diet promotes tumor ferroptosis but induces relative corticosterone deficiency that accelerates cachexia

Abstract The dependency of cancer cells on glucose can be targeted with high-fat low-carbohydrate ketogenic diet (KD). However, hepatic ketogenesis is suppressed in IL-6 producing cancers, which prevents the utilization of this nutrient source as energy for the organism. In two IL-6 associated murine models of cancer cachexia we describe delayed tumor growth but accelerated onset of cancer cachexia and shortened survival when mice are fed KD. Mechanistically, we find this uncoupling is a consequence of the biochemical interaction of two simultaneously occurring NADPH-dependent pathways. Within the tumor, increased production of lipid peroxidation products (LPPs) and, consequently, saturation of the glutathione (GSH) system leads to ferroptotic death of cancer cells. Systemically, redox imbalance and NADPH depletion impairs the biosynthesis of corticosterone, the main regulator of metabolic stress, in the adrenal glands. Administration of dexamethasone, a potent glucocorticoid, improves food intake, normalizes glucose homeostasis and utilization of nutritional substrates, delays onset of cancer cachexia and extends survival of tumor-bearing mice fed KD, while preserving reduced tumor growth. Our study highlights that the outcome of systemic interventions cannot necessarily be extrapolated from the effect on the tumor alone, but that they have to be investigated for anti-cancer and host effects. These findings may be relevant to clinical research efforts that investigate nutritional interventions such as KD in patients with cancer. Citation Format: Miriam Ferrer, Nicholas Mourikis, Emma E. Davidson, Sam O. Kleeman, Marta Zaccaria, Jill Habel, Rachel Rubino, Thomas R. Flint, Claire M. Connell, Michael J. Lukey, Eileen P. White, Anthony P. Coll, Ashok R. Venkitaraman, Tobias Janowitz. Ketogenic diet promotes tumor ferroptosis but induces relative corticosterone deficiency that accelerates cachexia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1162.

Effects of very low-carbohydrate ketogenic diets on lipid profiles in normal-weight (body mass index < 25 kg/m2) adults: a meta-analysis.

Very low-carbohydrate diets or ketogenic diets (KDs) have garnered attention for weight loss in patients with overweight or obesity as well as for normal-weight adults, yet the adverse effects of KDs, such as dyslipidemia in normal-weight adults, have not been studied extensively. This meta-analysis aimed to identify the effects of KDs on the lipid profile in normal-weight (body mass index [BMI] < 25 kg/m2) adults from randomized controlled trials. PubMed and Embase databases were searched on November 21, 2021, using search terms representing KDs and lipid profiles. Two researchers independently screened articles according to PICOS inclusion criteria. General study information, dietary data, and lipid profiles were extracted from eligible studies. Risk of bias was assessed using the Cochrane risk of bias 2 tool. Fixed- or random-effects meta-analysis was performed to estimate the effects of KDs on total cholesterol (TC), high-density lipoprotein-cholesterol (HDL-C), low-density lipoprotein-cholesterol (LDL-C), triglycerides, apolipoprotein A (apoA), and apolipoprotein B (apoB), considering heterogeneity across studies. The certainty of evidence was assessed using the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach. Three studies were selected for meta-analysis. A KD significantly increased TC by 1.47 mmol/L (95%CI, 0.72-2.22 mmol/L), LDL-C by 1.08 mmol/L (95%CI, 0.37-1.79 mmol/L), and apoB by 0.35 g/L (95%CI, 0.06-0.65 g/L). In addition, a KD significantly increased HDL-C by 0.35 mmol/L (95%CI, 0.27-0.42 mmol/L) and apoA by 0.34 g/L (95%CI, 0.28-0.41 g/L) compared with control diets. Triglyceride levels were not significantly different between KDs and control diets (P = 0.63). This study suggests unfavorable effects of KDs on TC and LDL-C in normal-weight adults. Although an increase in HDL-C can compensate for unfavorable changes in lipids, normal-weight individuals should consider the risk of hypercholesterolemia when consuming a KD. Results for triglycerides were inconsistent.