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A ketogenic diet lowers myocardial fatty acid oxidation but does not affect oxygen consumption: a study in overweight humans.
Luong, TV, Pedersen, MGB, Abild, CB, Cunnane, SC, Croteau, E, Lauritsen, KM, Kjaerulff, MLG, Tolbod, LP, Møller, N, Søndergaard, E, et al
Obesity (Silver Spring, Md.). 2024;(3):506-516
Abstract
OBJECTIVE A ketogenic diet (KD) characterized by very low carbohydrate intake and high fat consumption may simultaneously induce weight loss and be cardioprotective. The "thrifty substrate hypothesis" posits that ketone bodies are more energy efficient compared with other cardiac oxidative substrates such as fatty acids. This work aimed to study whether a KD with presumed increased myocardial ketone body utilization reduces cardiac fatty acid uptake and oxidation, resulting in decreased myocardial oxygen consumption (MVO2 ). METHODS This randomized controlled crossover trial examined 11 individuals with overweight or obesity on two occasions: (1) after a KD and (2) after a standard diet. Myocardial free fatty acid (FFA) oxidation, uptake, and esterification rate were measured using dynamic [11 C]palmitate positron emission tomography (PET)/computed tomography, whereas MVO2 and myocardial external efficiency (MEE) were measured using dynamic [11 C]acetate PET. RESULTS The KD increased plasma β-hydroxybutyrate, reduced myocardial FFA oxidation (p < 0.01) and uptake (p = 0.03), and increased FFA esterification (p = 0.03). No changes were observed in MVO2 (p = 0.2) or MEE (p = 0.87). CONCLUSIONS A KD significantly reduced myocardial FFA uptake and oxidation, presumably by increasing ketone body oxidation. However, this change in cardiac substrate utilization did not improve MVO2 , speaking against the thrifty substrate hypothesis.
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A ketogenic intervention improves dorsal attention network functional and structural connectivity in mild cognitive impairment.
Roy, M, Edde, M, Fortier, M, Croteau, E, Castellano, CA, St-Pierre, V, Vandenberghe, C, Rheault, F, Dadar, M, Duchesne, S, et al
Neurobiology of aging. 2022;:77-87
Abstract
Ketones, the brain's alternative fuel to glucose, bypass the brain glucose deficit and improve cognition in mild cognitive impairment (MCI). Our goal was to assess the impact of a 6-month ketogenic intervention on the functional connectivity within eight major brain resting-state networks, and its possible relationship to improved cognitive outcomes in the BENEFIC trial. MCI participants were randomized to a placebo (n = 15) or ketogenic medium chain triglyceride (kMCT; n = 17) intervention. kMCT was associated with increased functional connectivity within the dorsal attention network (DAN), which correlated to improvement in cognitive tests targeting attention. Ketone uptake (11C-acetoacetate PET) specifically in DAN cortical regions was highly increased in the kMCT group and was directly associated with the improved DAN functional connectivity. Analysis of the structural connectome revealed increased fiber density within the DAN following kMCT. Our findings suggest that ketones in MCI may prove beneficial for cognition at least in part because they improve brain network energy status, functional connectivity and axonal integrity.
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Ketones: potential to achieve brain energy rescue and sustain cognitive health during ageing.
Myette-Côté, É, Soto-Mota, A, Cunnane, SC
The British journal of nutrition. 2022;(3):407-423
Abstract
Alzheimer’s disease (AD) is the most common major neurocognitive disorder of ageing. Although largely ignored until about a decade ago, accumulating evidence suggests that deteriorating brain energy metabolism plays a key role in the development and/or progression of AD-associated cognitive decline. Brain glucose hypometabolism is a well-established biomarker in AD but was mostly assumed to be a consequence of neuronal dysfunction and death. However, its presence in cognitively asymptomatic populations at higher risk of AD strongly suggests that it is actually a pre-symptomatic component in the development of AD. The question then arises as to whether progressive AD-related cognitive decline could be prevented or slowed down by correcting or bypassing this progressive ‘brain energy gap’. In this review, we provide an overview of research on brain glucose and ketone metabolism in AD and its prodromal condition – mild cognitive impairment (MCI) – to provide a clearer basis for proposing keto-therapeutics as a strategy for brain energy rescue in AD. We also discuss studies using ketogenic interventions and their impact on plasma ketone levels, brain energetics and cognitive performance in MCI and AD. Given that exercise has several overlapping metabolic effects with ketones, we propose that in combination these two approaches might be synergistic for brain health during ageing. As cause-and-effect relationships between the different hallmarks of AD are emerging, further research efforts should focus on optimising the efficacy, acceptability and accessibility of keto-therapeutics in AD and populations at risk of AD.
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A ketogenic drink improves cognition in mild cognitive impairment: Results of a 6-month RCT.
Fortier, M, Castellano, CA, St-Pierre, V, Myette-Côté, É, Langlois, F, Roy, M, Morin, MC, Bocti, C, Fulop, T, Godin, JP, et al
Alzheimer's & dementia : the journal of the Alzheimer's Association. 2021;17(3):543-552
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Plain language summary
Brain energy rescue is emerging as a potential strategy to reduce cognitive decline in mild cognitive impairment (MCI) and Alzheimer’s disease (AD). The main aim of this study was to report the complete cognitive outcomes of the BENEFIC (Brain Energy, Functional Imaging, and Cognition) trial. The secondary objectives are to report plasma ketones (free caprylic and capric acids) levels; as well as the metabolic response, safety, and tolerability after the 6-month intervention. This study is a 6-month randomised, placebo-controlled trial. A total of 122 participants were enrolled and randomised into one of the two arms: ketogenic medium chain triglyceride (kMCT) or placebo arm. Results show that performance on widely used tests of episodic memory, executive function, and language improved over 6 months in MCI when consuming 30g/day of a kMCT drink relative to a matching placebo. Moderate to large effect sizes were observed on four cognitive tests in the kMCT group. Furthermore, it is safe and feasible for an MCI population to consume a 15g kMCT supplement twice daily for 6 months. Authors conclude that formulation of a kMCT drink improved four cognitive outcomes in MCI by increasing blood ketone levels.
Expert Review
Conflicts of interest:
None
Take Home Message:
- MCT supplementation is a promising strategy to rescue energy metabolism in the brain for those with MCIs by providing an alternative energy source
- Improvements in cognition were associated with increased blood ketone levels from MCT supplementation
- Practitioners should be mindful that higher intakes of MCTs (>30g/d) may lead to negative GI effects in some individuals.
Evidence Category:
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X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
This randomized controlled trial demonstrates that supplementation of a ketogenic drink containing medium-chain triglycerides (MCTs) is both safe and effective in improving cognitive outcomes in individuals with mild cognitive impairments (MCI), and does so through supporting energy metabolism in the brain.
Clinical practice applications:
These findings might be useful for Nutritional Therapists and Clinical Practitioners as follows:
- The results of this randomised controlled trial demonstrate that MCT supplementation (at 30g per day, split between two doses) is a viable strategy to support brain metabolism in individuals experiencing MCIs
- There was a dose-dependant response on elevated ketones and selected cognitive improvements which may have pertinent applications to therapeutic practice (either dietary or supplemental)
- The paper highlighted the involvement of energy metabolism in cognitive decline; this has potential therapeutic applications in terms of targeted nutritional support for mitochondrial function or energy signalling
- Some individuals experienced negative gastrointestinal effects when consuming MCTs at 30g/d for prolonged periods; practitioners should be mindful of this.
Considerations for future research:
Future research should consider:
- Whether dietary-induced ketosis can therapeutically impact MCI and support patient well-being
- Use of MCTs in those with severe cognitive impairments or those taking medication such as cholinesterase inhibitors
the role of glucose hypometabolism to determine alternative strategies for those who have GI issues with MCTs
- Whether APOE4 status has any impact on therapeutic outcomes to MCT supplementation
- Whether adjunct nutritional support for mitochondrial function alongside MCT could further impact on MCIs.
Abstract
INTRODUCTION Counteracting impaired brain glucose metabolism with ketones may improve cognition in mild cognitive impairment (MCI). METHODS Cognition, plasma ketone response, and metabolic profile were assessed before and 6 months after supplementation with a ketogenic drink containing medium chain triglyceride (ketogenic medium chain triglyceride [kMCT]; 15 g twice/day; n = 39) or placebo (n = 44). RESULTS Free and cued recall (Trial 1; P = .047), verbal fluency (categories; P = .024), Boston Naming Test (total correct answers; P = .033), and the Trail-Making Test (total errors; P = .017) improved significantly in the kMCT group compared to placebo (analysis of covariance; pre-intervention score, sex, age, education, and apolipoprotein E4 as covariates). Some cognitive outcomes also correlated positively with plasma ketones. Plasma metabolic profile and ketone response were unchanged. CONCLUSIONS This kMCT drink improved cognitive outcomes in MCI, at least in part by increasing blood ketone level. These data support further assessment of MCI progression to Alzheimer's disease.
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Mild cognitive impairment: when nutrition helps brain energy rescue-a report from the EuGMS 2020 Congress.
Cunnane, SC, Sieber, CC, Swerdlow, RH, Cruz-Jentoft, AJ
European geriatric medicine. 2021;(6):1285-1292
Abstract
BACKGROUND Mild cognitive impairment (MCI) is characterized by a decline in cognition and mainly affects older individuals above the age of 60. The global incidence of MCI varies, but it is often underdiagnosed and untreated. There is a distinct lack of approved pharmacologic options to treat MCI. There is, however, evidence to support the efficacy of nutritional interventions, such as ketogenic supplements/diets, which offer ketones as an alternative energy source to brain cells. This article explores the effect of ketones on metabolic activity in the brain and the mechanisms by which ketogenic medium-chain triglycerides (kMCTs) induce ketosis in patients with MCI. KEY TAKEAWAYS This article reviews the effect of ketogenic supplements/diets on brain metabolism, including evidence supporting the efficacy of ketones as an efficient fuel for the brain. It discusses the use of oral nutritional ketogenic supplements, with particular reference to the 6-month randomized controlled BENEFIC trial, which showed that consumption of a kMCT drink, BrainXpert Energy Complex, improved cognitive performance in individuals with MCI compared with placebo. CONCLUSION While there is a need for more long-term studies, results from the BENEFIC trial revealed the benefits of a brain-specific ketogenic supplement, as a nutritional intervention, on cognitive performance in individuals with MCI.
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The effect of a 6-month ketogenic medium-chain triglyceride supplement on plasma cardiometabolic and inflammatory markers in mild cognitive impairment.
Myette-Côté, É, St-Pierre, V, Beaulieu, S, Castellano, CA, Fortier, M, Plourde, M, Bocti, C, Fulop, T, Cunnane, SC
Prostaglandins, leukotrienes, and essential fatty acids. 2021;:102236
Abstract
INTRODUCTION Mild cognitive impairment (MCI) is often accompanied by metabolic abnormalities and inflammation that might play a role in the development of cognitive impairment. The use of ketogenic medium-chain triglycerides (kMCT) to improve cognition in this population has shown promising results but remains controversial because of the potentially detrimental effect of elevated intake of saturated fatty acids on cardiovascular (CV) health and perhaps inflammatory processes. The primary aim of this secondary data analysis report is to describe changes in cardiometabolic markers and peripheral inflammation during a 6-month kMCT intervention in MCI. METHODS Thirty-nine participants with MCI completed the intervention of 30 g/day of either a kMCT drink or calorie-matched placebo (high-oleic acid) for 6 months. Plasma concentrations of cardiometabolic and inflammatory markers were collected before (fasting state) and after the intervention (2 h following the last drink). RESULTS A mixed model ANOVA analysis revealed a time by group interaction for ketones (P < 0.001), plasma 8:0 and 10:0 acids (both P < 0.001) and IL-8 (P = 0.002) with follow up comparison revealing a significant increase in the kMCT group (+48%, P = 0.005), (+3,800 and +4,900%, both P < 0.001) and (+147%, P < 0.001) respectively. A main effect of time was observed for insulin (P = 0.004), triglycerides (P = 0.011) and non-esterified fatty acids (P = 0.036). CONCLUSION Under these study conditions, 30 g/d of kMCT taken for six months and up to 2-hour before post-intervention testing had minimal effect on an extensive profile of circulating cardiometabolic and inflammatory markers as compared to a placebo calorie-matched drink. Our results support the safety kMCT supplementation in individuals with MCI. The clinical significance of the observed increase in circulating IL-8 levels is presently unknown and awaits future studies.
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Seven-day overfeeding enhances adipose tissue dietary fatty acid storage and decreases myocardial and skeletal muscle dietary fatty acid partitioning in healthy subjects.
Noll, C, Montastier, É, Amrani, M, Kunach, M, Frisch, F, Fortin, M, Bouffard, L, Dubreuil, S, Phoenix, S, Cunnane, SC, et al
American journal of physiology. Endocrinology and metabolism. 2020;(2):E286-E296
Abstract
Increased myocardial partitioning of dietary fatty acids (DFA) and decreased left ventricular (LV) function is associated with insulin resistance in prediabetes. We hypothesized that enhanced myocardial DFA partitioning and reduced LV function might be induced concomitantly with reduced insulin sensitivity upon a 7-day hypercaloric (+50% in caloric intake), high-saturated fat (~11%energy), and simple carbohydrates (~54%energy) diet (HIGHCAL) versus an isocaloric diet (ISOCAL) with a moderate amount of saturated fat (~8%energy) and carbohydrates (~50%energy). Thirteen healthy subjects (7 men/6 women) underwent HIGHCAL versus ISOCAL in a randomized crossover design, with organ-specific DFA partitioning and LV function measured using the oral 14(R,S)-[18F]fluoro-6-thia-heptadecanoic acid and [11C]acetate positron emission tomography methods at the end of both interventions. HIGHCAL induced a decrease in insulin sensitivity indexes with no significant change in body composition. HIGHCAL led to increased subcutaneous abdominal (+4.2 ± 1.6%, P < 0.04) and thigh (+2.4 ± 1.2%, P < 0.08) adipose tissue storage and reduced cardiac (-0.31 ± 0.11 mean standard uptake value [(SUV), P < 0.03] and skeletal muscle (-0.17 ± 0.08 SUV, P < 0.05) DFA partitioning without change in LV function. We conclude that early increase in adipose tissue DFA storage protects the heart and skeletal muscles from potential deleterious effects of DFA.
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The conundrum of human immune system "senescence".
Pawelec, G, Bronikowski, A, Cunnane, SC, Ferrucci, L, Franceschi, C, Fülöp, T, Gaudreau, P, Gladyshev, VN, Gonos, ES, Gorbunova, V, et al
Mechanisms of ageing and development. 2020;:111357
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Abstract
There is a great deal of debate on the question of whether or not we know what ageing is (Ref. Cohen et al., 2020). Here, we consider what we believe to be the especially confused and confusing case of the ageing of the human immune system, commonly referred to as "immunosenescence". But what exactly is meant by this term? It has been used loosely in the literature, resulting in a certain degree of confusion as to its definition and implications. Here, we argue that only those differences in immune parameters between younger and older adults that are associated in some definitive manner with detrimental health outcomes and/or impaired survival prospects should be classed as indicators of immunosenescence in the strictest sense of the word, and that in humans we know remarkably little about their identity. Such biomarkers of immunosenescence may nonetheless indicate beneficial effects in other contexts, consistent with the notion of antagonistic pleiotropy. Identifying what could be true immunosenescence in this respect requires examining: (1) what appears to correlate with age, though generality across human populations is not yet confirmed; (2) what clearly is part of a suite of canonical changes in the immune system that happen with age; (3) which subset of those changes accelerates rather than slows aging; and (4) all changes, potentially population-specific, that accelerate agig. This remains an immense challenge. These questions acquire an added urgency in the current SARS-CoV-2 pandemic, given the clearly greater susceptibility of older adults to COVID-19.
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A short-term intervention combining aerobic exercise with medium-chain triglycerides (MCT) is more ketogenic than either MCT or aerobic exercise alone: a comparison of normoglycemic and prediabetic older women.
Vandenberghe, C, Castellano, CA, Maltais, M, Fortier, M, St-Pierre, V, Dionne, IJ, Cunnane, SC
Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme. 2019;(1):66-73
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Abstract
The objectives of this study were to determine (i) whether a 5-day aerobic exercise (AE) program combined with a medium-chain triglyceride (MCT) supplement would increase the plasma ketone response in older women more than either intervention alone and (ii) whether ketonemia after these combined or separate treatments was alike in normoglycemic (NG) and prediabetic (PD) women. Older women (NG, n = 10; PD, n = 9) underwent a 4-h metabolic study after each of 4 different treatments: (i) no treatment (control), (ii) 5 days of MCT alone (30 g·day-1), (iii) 1 session of 30 min of AE alone, and (iv) 5 days of MCT and AE combined (MCT+AE). Blood was sampled every 30 min over 4 h for analysis. In NG, MCT+AE induced the highest area under the curve (AUC) for plasma ketones (835 ± 341 μmol·h·L-1); this value was 69% higher than that observed with MCT alone (P < 0.05). AUCs were not different between MCT alone and MCT+AE in PD, but both treatments induced a significantly higher AUC than the control or AE alone (P < 0.05). Although there was a trend towards a higher ketone AUC in NG versus PD with AE alone (P = 0.091), there was no significant difference between the ketone AUCs in PD and NG. In conclusion, MCT+AE was more ketogenic in older women than MCT or AE alone. MCT+AE had a synergistic effect on ketonemia in NG but not in PD. Whether improving insulin sensitivity with a longer term AE intervention can improve the ketogenic effect of MCT in PD and thereby increase brain ketone uptake in older people merits further investigation.
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A 3-Month Aerobic Training Program Improves Brain Energy Metabolism in Mild Alzheimer's Disease: Preliminary Results from a Neuroimaging Study.
Castellano, CA, Paquet, N, Dionne, IJ, Imbeault, H, Langlois, F, Croteau, E, Tremblay, S, Fortier, M, Matte, JJ, Lacombe, G, et al
Journal of Alzheimer's disease : JAD. 2017;(4):1459-1468
Abstract
BACKGROUND Aerobic training has some benefits for delaying the onset or progression of Alzheimer's disease (AD). Little is known about the implication of the brain's two main fuels, glucose and ketones (acetoacetate), associated with thesebenefits. OBJECTIVE To determine whether aerobic exercise training modifies brain energy metabolism in mild AD. METHODS In this uncontrolled study, ten patients with mild AD participated in a 3-month, individualized, moderate-intensity aerobic training on a treadmill (Walking). Quantitative measurement of brain uptake of glucose (CMRglu) and acetoacetate (CMRacac) using neuroimaging and cognitive testing were done before and after the Walking program. RESULTS Four men and six women with an average global cognitive score (MMSE) of 26/30 and an average age of 73 y completed the Walking program. Average total distance and treadmill speed were 8 km/week and 4 km/h, respectively. Compared to the Baseline, after Walking, CMRacac was three-fold higher (0.6±0.4 versus 0.2±0.1 μmol/100 g/min; p = 0.01). Plasma acetoacetate concentration and the blood-to-brain acetoacetate influx rate constant were also increased by 2-3-fold (all p≤0.03). CMRglu was unchanged after Walking (28.0±0.1 μmol/100 g/min; p = 0.96). There was a tendency toward improvement in the Stroop-color naming test (-10% completion time, p = 0.06). Performance on the Trail Making A&B tests was also directly related to plasma acetoacetate and CMRacac (all p≤0.01). CONCLUSION In mild AD, aerobic training improved brain energy metabolism by increasing ketone uptake and utilization while maintaining brain glucose uptake, and could potentially be associated with some cognitive improvement.