ECSS Paris 2023: OP-PN08
INTRODUCTION: The ketogenic diet (KD) is a nutritional approach, commonly recognized for its efficacy in promoting fat loss, characterized by a high fat content, an adequate protein intake, and restricted carbohydrate consumption (<50 grams per day). However, the metabolic adaptations promoted by KD may potentially contrast with the pathways that regulate the hypertrophic response. Indeed, the KD mimics several effects of caloric restriction by enhancing the activity of key factors involved in fat oxidation and oxidative phosphorylation. Among these factors, AMP-activated protein kinase (AMPK) stimulates mitochondrial activity while concurrently inhibiting the mechanistic target of rapamycin (mTOR), a critical regulator of protein synthesis. In this regard, the aim of this study is to investigate the impact of the KD on the muscular response to resistance training in trained male subjects. METHODS: Eight healthy trained male adults (29.9 ± 8.7 years) have been enrolled and randomly divided into a ketogenic diet (KD) or control diet (CD) group. Both diets were similar for energy (35 kcal/kg bw) and protein content (2 g/kg bw). All participants performed the same resistance training (RT) protocol for 4 weeks. Resting metabolic rate, body composition (Dual-energy X-ray absorptiometry), total body water (TBW via bioelectrical impedance analysis), quadriceps cross-sectional area via ultrasound and muscle strength were assessed at baseline and after 4 weeks of RT. In addition, muscle biopsies from the vastus lateralis were sampled at rest, 6 and 24 hours after a single bout of RT performed before and after 4 weeks of intervention. Histological data and phosphorylation of regulatory signaling proteins (i.e., mTOR, 4EBP1, and S6K) are under evaluation. RESULTS: Preliminary data confirmed that participants in the KD group enhanced fat oxidation compared to the CD group (-12% vs. -6% mean decrease in respiratory ratio). Fat free mass was not significantly affected by the intervention in both groups. However, pronounced fat loss was reported in KD groups (-2,3 kg vs. +0,6 kg). In the KD group, a fluid loss was observed (-3% vs. 0% mean changes in TBW). CONCLUSION: According to these preliminary results, KD seems to improve body composition without impacting gains in fat-free mass or muscle force. Further analysis of biopsies samples will show the effect of KD on histological parameters and hypertrophic signaling after RT.
Read CV Giuseppe CerulloECSS Paris 2023: OP-PN08
INTRODUCTION: Altitude-related decrease in ambient pressure results in reduced oxygen availability for mitochondrial respiration. This leads to augmented physiological strain and decreased exercise capacity (1). To counteract this, ventilation, cardiac output, as well as muscle and lung blood perfusion are increased (2). However, even long-term acclimatisation at high altitudes does not fully counteract the negative effects of hypobaric hypoxia (2). Interestingly, we recently showed that elevating blood ketone bodies via oral ketone ester intake can attenuate the decline in blood and muscle oxygenation, while increasing oxygen uptake during submaximal cycling exercise at a simulated altitude of 2500–3000 m (3). In the present work we aimed to investigate whether ketone ester intake can attenuate the drop in blood and muscle oxygenation and subsequently alleviate the reduction of cycling exercise capacity during terrestrial high-altitude sojourn. METHODS: Thirty-four participants (28 males, 6 females) underwent two experimental trials, one near sea level (295 m; Ljubljana, Slovenia) and one on the 3rd day of a high-altitude sojourn (3375 m; Torino hut, Aosta Valley, Italy). During the high-altitude sojourn, participants received, in randomized order, either a placebo (PLA group, n = 17) or ketone ester (KE group, n = 17) – with the aim to intermittently elevate blood ketone (e.g., D-ß-hydroxybutyrate ([ßHB])) levels to ~2–4 mM. Minute ventilation, oxygen uptake, systemic oxygen saturation and muscle tissue oxygenation, were continuously measured at rest, across submaximal work rates, and at peak exercise during the ramp-wise incremental cycling test (1 W increment per 3 s) to volitional exhaustion. Independent t-tests with a Bonferroni correction were employed to evaluate differences between groups with significance set a-priori at p < 0.05. RESULTS: KE ingestion resulted in stable ketosis (blood [ßHB] of ~2–4 mM in KE) at altitude, while blood [ßHB] remained low (~0.3 mM) in the PLA group (p < 0.05 for KE vs. PLA). No differences between groups were observed for hypoxia-related changes in oxygen uptake, systemic oxygen saturation and muscle tissue oxygenation or concomitant increase in minute ventilation at all relative power outputs. Also, no differences in altitude-related exercise capacity reduction were noted between groups (KE: Δ50 ± 16W vs. PLA: Δ53 ± 20 W, p = 0.999). CONCLUSION: These data suggest that exogenous ketosis induced by ketone ester ingestion does not attenuate high-altitude related drop in blood and muscle oxygenation nor cycling exercise capacity.
Read CV Domen TominecECSS Paris 2023: OP-PN08
INTRODUCTION: Exogenous ketosis is proposed to enhance exercise performance & recovery. Ingestion of the ketone monoester (KME) rapidly raises blood ketone body levels & reduces postprandial glucose in healthy individuals. Glucose is a principle substrate for hepatic de novo lipogenesis (DNL) with elevated availability upregulating DNL. We hypothesised that KME-induced blood glucose suppression would lower postprandial DNL. METHODS: Ten adults free from metabolic disease (6F/4M; age: 28 ± 2 yr; BMI: 23.8 ± 1.1 kg·m-2; mean ± SEM) underwent two 7 hr postprandial study days. For two days prior to each visit they were prescribed a eucaloric high-sugar diet (404 ± 31 g·day-1 carbohydrate; 55.5% as sugar) to upregulate hepatic DNL. They additionally consumed heavy water (D2O) on the evening preceding each visit (~0.4% plasma enrichment). After an overnight fast, participants ingested a mixed-nutrient breakfast meal that provided 2 g·kg-1 bodyweight of carbohydrate (891.7 ± 80.9 kcal; 65.5% total kcal from carbohydrate, 10.0% protein, 24.5% fat). At 1 hr post-meal, either a KME (573 mg·kg-1) or a taste & volume-matched placebo (PLA) drink was consumed in a blinded & randomised-counterbalanced crossover manner. Venous blood samples were collected when fasted & over the postprandial period. Hepatic DNL was quantified as the incorporation of deuterium into newly synthesised palmitate (16:0) within very low-density lipoprotein-triglyceride (VLDL-TG), determined by gas-chromatography mass-spectrometry. Data were analysed by paired t-tests & two-way (time & condition) repeated-measures ANOVAs. Significance was set at p<0.05. RESULTS: Plasma [ß-hydroxybutyrate] was elevated by KME with greater concentrations observed from 15 to 300 min post-drink (p=0.03; KME: 3.14 ± 0.42, PLA: 0.05 ± 0.01 mM). Plasma [glucose] was reduced after the KME drink, with AUCs 7.4% lower compared to PLA (p<0.001). Postprandial insulinaemia was unaffected by KME. There were distinct differences in hepatic DNL, such that KME increased DNL at 360 min post-drink (absolute increase, 13.9%; p=0.01) with a tendency to also be greater at 180 min (8.8%, p=0.09). KME did not affect plasma [VLDL-TG] nor the proportion of palmitate or other fatty acids within VLDL-TG (mol%). Both plasma [non-esterified fatty acid] & [glycerol] were suppressed during the latter stages of the feeding test under KME (p=0.04). There were no differences between KME & PLA conditions for plasma [triglyceride] or [lactate], nor for respiratory quotient. CONCLUSION: This study demonstrates that postprandial hepatic DNL is elevated under exogenous ketosis in healthy adults, despite lowered circulating glucose levels & insulin being unaffected. This might have pathological implications as the development of MASLD & hepatic insulin resistance have been associated with elevated DNL. Future work investigating the influence of exogenous ketosis on DNL during exercise and under chronic exposure to KME is warranted to better inform athletes consuming ketone supplements.
Read CV Adam IsherwoodECSS Paris 2023: OP-PN08