Ketones for Post-exercise Recovery: Potential Applications and Mechanisms

Muscle transcriptome profiles in elite male ultra-endurance athletes acclimated to a high-carbohydrate versus low-carbohydrate diet

Low-carbohydrate, high-fat diets enhance lipid metabolism and decrease reliance on glucose oxidation in athletes, but the associated gene expression patterns remain unclear. The purpose of this study was to determine whether coordinated molecular pathways in skeletal muscle may be revealed by differential expression of genes driven by dietary profile, exercise, and/or their interaction. We investigated the skeletal muscle transcriptome in elite ultra-endurance athletes habitually (~ 20 months) consuming a high-carbohydrate, low-fat (HC, n = 10, 33 ± 6y, VO2max = 63.4 ± 6.2 mL O2•kg-1•min-1) or low-carbohydrate, high-fat (LC, n = 10, 34 ± 7y, VO2max = 64.7 ± 3.7 mL O2•kg-1•min-1) diet. Skeletal muscle gene expression was measured at baseline (BL), immediately-post (H0), and 2 h (H2) after 3 h submaximal treadmill running. Diet induced a coordinated but divergent expression pattern at BL where LC had higher expression of genes associated with lipid metabolism. Exercise resulted in a dynamic but uniform gene response, with no major differences between groups (H0). At H2, gene expression patterns were associated with differential pathway activity, including inflammation/immunity, suggesting a diet-specific influence on early muscle recovery. These results indicate that low-carbohydrate, high-fat diets lead to differences in resting and exercise-induced skeletal muscle gene expression patterns, underlying our previous findings of differential fuel utilization in elite ultra-endurance athletes.

Three Weeks on a Ketogenic Diet Reduces Free Testosterone and Free Estradiol in Middle-Aged Obese Men and Women

Background

Beta-hydroxybuturate (β-OHB) supplements are commonly utilized in sports by both recreational and professional athletes. In a recent study, we observed a drop in testosterone levels following the oral ingestion of racemic sodium-β-OHB. In this investigation, we aim to determine whether a single oral dose of ketone ester (study I) and prolonged endogenous ketosis (study II) also reduces testosterone levels.

Design

This investigation integrated samples from two distinct studies. Study I was a randomized, controlled, crossover trial with ten healthy, young male participants receiving either a weight-adjusted ketone ester or control (water, CTR) and vice versa following an overnight fast. Repeated blood sampling was used to monitor plasma β-OHB and testosterone levels. Study II, another randomized, controlled, crossover trial, included 11 middle-aged participants (five males). They followed either a ketogenic diet (KD) characterized by low carbohydrates and high fat content or a standard diet (SDD) for three weeks. After each study period, participants underwent examination following an overnight fast, with repeated measures employed to analyze concentrations of plasma β-OHB and sex hormone levels.

Results

Study I: Testosterone decreased from 23.8 ± 2.4 nmol/l to 22.3 ± 2.5 nmol/l 300 minutes after the ketone ester and increased from 20.9 ± 2.1 nmol/l to 22.2 ± 1.9 300 minutes after CTR. This difference was not significant, p = 0.06. Study II. Total testosterone was unaffected after the KD compared to the SDD in men (20.2 ± 1.23 nmol/l vs. 18.2 ± 1.23 nmol/l (p = 0.1)) and was lower after KD in women (0.87 ± 0.06 vs. 1.1 ± 0.06 nmol/l (p < 0.0001)). Sex hormone-binding globulin (SHBG) increased in men after KD compared with SDD (31.2 ± 2.6 nmol/l vs 25.0 ± 2.6 nmol/l, p < 0.0001) and women (26.5 ± 3.05 nmol/l vs 24.2 ± 3.05 nmol/l, p = 0.003). The free androgen index decreased after KD in men (ratio: 0.65 ± 0.05 vs. ratio: 0.74 ± 0.05, p = 0.04) and in women (ratio: 0.036 ± 0.006 vs. SDD 0.05 ± 0.006, p = 0.0001). Free estradiol index was also found lower after KD in men (ratio: 3.1 ± 0.8 vs. ratio: 4.8 ± 0.8, p = 0.0003) and in women (ratio: 1.2 ± 2.2 vs. 9.8 ± 2.2, p = 0.0001).

Conclusion

Our findings indicate that the acute ingestion of ketone ester may not reduce testosterone levels in healthy young males. However, a three-week exposure to KB from a KD results in an increase in SHBG in men and women with obesity as well as it lowers free testosterone and estradiol for men and women. We thus present evidence of crosstalk between alterations in a metabolite, β-OHB, and the regulation of the hypothalamic-pituitary-gonadal axis from a KD. The clinical impact of this reduction remains to be investigated. This trial is registered with NCT04156477 and NCT05012748.

Metabolic alterations and cellular responses to β-Hydroxybutyrate treatment in breast cancer cells

BACKGROUND

The ketogenic diet (KD), based on high fat (over 70% of daily calories), low carbohydrate, and adequate protein intake, has become popular due to its potential therapeutic benefits for several diseases including cancer. Under KD and starvation conditions, the lack of carbohydrates promotes the production of ketone bodies (KB) from fats by the liver as an alternative source of metabolic energy. KD and starvation may affect the metabolism in cancer cells, as well as tumor characteristics. The aim of this study is to evaluate the effect of KD conditions on a wide variety of aspects of breast cancer cells in vitro.

METHODS

Using two cancer and one non-cancer breast cell line, we evaluate the effect of β-hydroxybutyrate (βHb) treatment on cell growth, survival, proliferation, colony formation, and migration. We also assess the effect of KB on metabolic profile of the cells. Using RNAseq analysis, we elucidate the effect of βHb on the gene expression profile.

RESULTS

Significant effects were observed following treatment by βHb which include effects on viability, proliferation, and colony formation of MCF7 cells, and different effects on colony formation of MDA-MB-231 cells, with no such effects on non-cancer HB2 cells. We found no changes in glucose intake or lactate output following βHb treatment as measured by LC-MS, but an increase in reactive oxygen species (ROS) level was detected. RNAseq analysis demonstrated significant changes in genes involved in lipid metabolism, cancer, and oxidative phosphorylation.

CONCLUSIONS

Based on our results, we conclude that differential response of cancer cell lines to βHb treatment, as alternative energy source or signal to alter lipid metabolism and oncogenicity, supports the need for a personalized approach to breast cancer patient treatment.

Understanding the variation in exercise responses to guide personalized physical activity prescriptions

Understanding the factors that contribute to exercise response variation is the first step in achieving the goal of developing personalized exercise prescriptions. This review discusses the key molecular and other mechanistic factors, both extrinsic and intrinsic, that influence exercise responses and health outcomes. Extrinsic characteristics include the timing and dose of exercise, circadian rhythms, sleep habits, dietary interactions, and medication use, whereas intrinsic factors such as sex, age, hormonal status, race/ethnicity, and genetics are also integral. The molecular transducers of exercise (i.e., genomic/epigenomic, proteomic/post-translational, transcriptomic, metabolic/metabolomic, and lipidomic elements) are considered with respect to variability in physiological and health outcomes. Finally, this review highlights the current challenges that impede our ability to develop effective personalized exercise prescriptions. The Molecular Transducers of Physical Activity Consortium (MoTrPAC) aims to fill significant gaps in the understanding of exercise response variability, yet further investigations are needed to address additional health outcomes across all populations.

High-fat ketogenic diets and ketone monoester supplements differentially affect substrate metabolism during aerobic exercise

Chronically adhering to high-fat ketogenic diets or consuming ketone monoester supplements elicits ketosis. Resulting changes in substrate metabolism appear to be drastically different between ketogenic diets and ketone supplements. Consuming a ketogenic diet increases fatty acid oxidation with concomitant decreases in endogenous carbohydrate oxidation. Increased fat oxidation eventually results in an accumulation of circulating ketone bodies, which are metabolites of fatty acids that serve as an alternative source of fuel. Conversely, consuming ketone monoester supplements rapidly increases circulating ketone body concentrations that typically exceed those achieved by adhering to ketogenic diets. Rapid increases in ketone body concentrations with ketone monoester supplementation elicit a negative feedback inhibition that reduces fatty acid mobilization during aerobic exercise. Supplement-derived ketosis appears to have minimal impact on sparing of muscle glycogen or minimizing of carbohydrate oxidation during aerobic exercise. This review will discuss the substrate metabolic and associated aerobic performance responses to ketogenic diets and ketone supplements.

An open-label, acute clinical trial in adults to assess ketone levels, gastrointestinal tolerability, and sleepiness following consumption of (R)-1,3-butanediol (Avela™)

Introduction: A study was undertaken to determine the acute effects of a beverage made with Avela™ (R)-1,3-butanediol, on blood beta-hydroxybutyrate (BHB) levels (using the Keto-Mojo monitor), gastrointestinal (GI) tolerability (using the modified visual analogue scale GI Symptoms Tool), and sleepiness (using the Stanford Sleepiness Scale). Methods: Following a 12-h overnight fast, 26 healthy adults consumed one beverage containing 11.5 g of (R)-1,3-butanediol at each of 0, 30, and 60 min, culminating in a total intake of 34.5 g of (R)-1,3-butanediol. Blood BHB levels, GI tolerability, and sleepiness were assessed at baseline (0 min), and at 30, 60, 90, 120, 180, 240, and 300 min. At 240 min, a protein bar was consumed. Results: The mean (±SD) BHB fasting baseline level, maximal concentration, time at maximal concentration, and incremental area under the curve over 300 min were 0.23 ± 0.21 mmol/L, 2.10 ± 0.97 mmol/L, 133.85 ± 57.07 min, and 376.73 ± 156.76 mmol/L*min, respectively. BHB levels at each time point were significantly increased relative to baseline. In females, BHB T_max was significantly greater (p = 0.046), and BHB iAUC_0-300 min nearly significantly greater (p = 0.06) than in males. Discussion: The beverage formulated with Avela™ had no impact on sleepiness and was generally well-tolerated, with no or mild GI symptoms reported in most participants. Mild headaches were reported as an adverse event by five participants and judged possibly related to the study product in two of the participants.

Exogenous Ketones and Lactate as a Potential Therapeutic Intervention for Brain Injury and Neurodegenerative Conditions

Metabolic dysfunction is a ubiquitous underlying feature of many neurological conditions including acute traumatic brain injuries and chronic neurodegenerative conditions. A central problem in neurological patients, in particular those with traumatic brain injuries, is an impairment in the utilization of glucose, which is the predominant metabolic substrate in a normally functioning brain. In such patients, alternative substrates including ketone bodies and lactate become important metabolic candidates for maintaining brain function. While the potential neuroprotective benefits of ketosis have been recognized for up to almost a century, the majority of work has focused on the use of ketogenic diets to induce such a state, which is inappropriate in cases of acute disease due to the prolonged periods of time (i.e., weeks to months) required for the effects of a ketogenic diet to be seen. The following review seeks to explore the neuroprotective effects of exogenous ketone and lactate preparations, which have more recently become commercially available and are able to induce a deep ketogenic response in a fraction of the time. The rapid response of exogenous preparations makes their use as a therapeutic adjunct more feasible from a clinical perspective in both acute and chronic neurological conditions. Potentially, their ability to globally moderate long-term, occult brain dysfunction may also be relevant in reducing lifetime risks of certain neurodegenerative conditions. In particular, this review explores the association between traumatic brain injury and contusion-related dementia, assessing metabolic parallels and highlighting the potential role of exogenous ketone and lactate therapies.

Exogenous Ketone Supplements in Athletic Contexts: Past, Present, and Future

The ketone bodies acetoacetate (AcAc) and β-hydroxybutyrate (βHB) have pleiotropic effects in multiple organs including brain, heart, and skeletal muscle by serving as an alternative substrate for energy provision, and by modulating inflammation, oxidative stress, catabolic processes, and gene expression. Of particular relevance to athletes are the metabolic actions of ketone bodies to alter substrate utilisation through attenuating glucose utilisation in peripheral tissues, anti-lipolytic effects on adipose tissue, and attenuation of proteolysis in skeletal muscle. There has been long-standing interest in the development of ingestible forms of ketone bodies that has recently resulted in the commercial availability of exogenous ketone supplements (EKS). These supplements in the form of ketone salts and ketone esters, in addition to ketogenic compounds such as 1,3-butanediol and medium chain triglycerides, facilitate an acute transient increase in circulating AcAc and βHB concentrations, which has been termed 'acute nutritional ketosis' or 'intermittent exogenous ketosis'. Some studies have suggested beneficial effects of EKS to endurance performance, recovery, and overreaching, although many studies have failed to observe benefits of acute nutritional ketosis on performance or recovery. The present review explores the rationale and historical development of EKS, the mechanistic basis for their proposed effects, both positive and negative, and evidence to date for their effects on exercise performance and recovery outcomes before concluding with a discussion of methodological considerations and future directions in this field.

On the nutritional and therapeutic effects of ketone body D-β-hydroxybutyrate

Abstract

d-β-hydroxybutyrate (d-3HB), a monomer of microbial polyhydroxybutyrate (PHB), is also a natural ketone body produced during carbohydrate deprivation to provide energy to the body cells, heart, and brain. In recent years, increasing evidence demonstrates that d-3HB can induce pleiotropic effects on the human body which are highly beneficial for improving physical and metabolic health. Conventional ketogenic diet (KD) or exogenous ketone salts (KS) and esters (KE) have been used to increase serum d-3HB level. However, strict adaptation to the KD was often associated with poor patient compliance, while the ingestion of KS caused gastrointestinal distresses due to excessive consumption of minerals. As for ingestion of KE, subsequent degradation is required before releasing d-3HB for absorption, making these methods somewhat inferior. This review provides novel insights into a biologically synthesized d-3HB (d-3-hydroxybutyric acid) which can induce a faster increase in plasma d-3HB compared to the use of KD, KS, or KE. It also emphasizes on the most recent applications of d-3HB in different fields, including its use in improving exercise performance and in treating metabolic or age-related diseases. Ketones may become a fourth micro-nutrient that is necessary to the human body along with carbohydrates, proteins, and fats. Indeed, d-3HB being a small molecule with multiple signaling pathways within the body exhibits paramount importance in mitigating metabolic and age-related diseases. Nevertheless, specific dose–response relationships and safety margins of using d-3HB remain to be elucidated with more research.

Key points

• d-3HB induces pleiotropic effects on physical and metabolic health.

• Exogenous ketone supplements are more effective than ketogenic diet.

• d-3HB as a ketone supplement has long-term healthy impact.