A Low-Carbohydrate Ketogenic Diet and Treadmill Training Enhanced Fatty Acid Oxidation Capacity but Did Not Enhance Maximal Exercise Capacity in Mice.

The low-carbohydrate ketogenic diet (LCKD) is a dietary approach characterized by the intake of high amounts of fat, a balanced amount of protein, and low carbohydrates, which is insufficient for metabolic demands. Previous studies have shown that an LCKD alone may contribute to fatty acid oxidation capacity, along with endurance. In the present study, we combined a 10-week LCKD with an 8-week forced treadmill running program to determine whether training in conjunction with LCKD enhanced fatty acid oxidation capacity, as well as whether the maximal exercise capacity would be affected by an LCKD or training in a mice model. We found that the lipid pool and fatty acid oxidation capacity were both enhanced following the 10-week LCKD. Further, key fatty acid oxidation related genes were upregulated. In contrast, the 8-week training regimen had no effect on fatty acid and ketone body oxidation. Key genes involved in carbohydrate utilization were downregulated in the LCKD groups. However, the improved fatty acid oxidation capacity did not translate into an enhanced maximal exercise capacity. In summary, while favoring the fatty acid oxidation system, an LCKD, alone or combined with training, had no beneficial effects in our intensive exercise-evaluation model. Therefore, an LCKD may be promising to improve endurance in low- to moderate-intensity exercise, and may not be an optimal choice for those partaking in high-intensity exercise.

Ketone Body, 3-Hydroxybutyrate: Minor Metabolite - Major Medical Manifestations.

Ketone bodies - 3-hydroxybutyrate (3-OHB), acetoacetate, and acetone - are ancient, evolutionarily preserved, small fuel substrates, which uniquely can substitute and alternate with glucose under conditions of fuel and food deficiency. Once canonized as a noxious, toxic pathogen leading to ketoacidosis in patients with diabetes, it is now becoming increasingly clear that 3-OHB possesses a large number of beneficial, life-preserving effects in the fields of clinical science and medicine. 3-OHB, the most prominent ketone body, binds to specific hydroxyl-carboxylic acid receptors and inhibits histone deacetylase enzymes, free fatty acid receptors, and the NOD-like receptor protein 3 inflammasome, tentatively inhibiting lipolysis, inflammation, oxidative stress, cancer growth, angiogenesis, and atherosclerosis, and perhaps contributing to the increased longevity associated with exercise and caloric restriction. Clinically ketone bodies/ketogenic diets have for a long time been used to reduce the incidence of seizures in epilepsy and may have a role in the treatment of other neurological diseases such as dementia. 3-OHB also acts to preserve muscle protein during systemic inflammation and is an important component of the metabolic defense against insulin-induced hypoglycemia. Most recently, a number of studies have reported that 3-OHB dramatically increases myocardial blood flow and cardiac output in control subjects and patients with heart failure. At the moment, scientific interest in ketone bodies, in particular 3-OHB, is in a hectic transit and, hopefully, future, much needed, controlled clinical studies will reveal and determine to which extent the diverse biological manifestations of 3-OHB should be introduced medically.

Ketone Bodies Attenuate Wasting in Models of Atrophy.

BACKGROUND: Cancer Anorexia Cachexia Syndrome (CACS) is a distinct atrophy disease negatively influencing multiple aspects of clinical care and patient quality of life. Although it directly causes 20% of all cancer-related deaths, there are currently no model systems that encompass the entire multifaceted syndrome, nor are there any effective therapeutic treatments. METHODS: A novel model of systemic metastasis was evaluated for the comprehensive CACS (metastasis, skeletal muscle and adipose tissue wasting, inflammation, anorexia, anemia, elevated protein breakdown, hypoalbuminemia, and metabolic derangement) in both males and females. Ex vivo skeletal muscle analysis was utilized to determine ubiquitin proteasome degradation pathway activation. A novel ketone diester (R/S 1,3-Butanediol Acetoacetate Diester) was assessed in multifaceted catabolic environments to determine anti-atrophy efficacy. RESULTS: Here, we show that the VM-M3 mouse model of systemic metastasis demonstrates a novel, immunocompetent, logistically feasible, repeatable phenotype with progressive tumor growth, spontaneous metastatic spread, and the full multifaceted CACS with sex dimorphisms across tissue wasting. We also demonstrate that the ubiquitin proteasome degradation pathway was significantly upregulated in association with reduced insulin-like growth factor-1/insulin and increased FOXO3a activation, but not tumor necrosis factor-α-induced nuclear factor-kappa B activation, driving skeletal muscle atrophy. Additionally, we show that R/S 1,3-Butanediol Acetoacetate Diester administration shifted systemic metabolism, attenuated tumor burden indices, reduced atrophy/catabolism and mitigated comorbid symptoms in both CACS and cancer-independent atrophy environments. CONCLUSIONS: Our findings suggest the ketone diester attenuates multifactorial CACS skeletal muscle atrophy and inflammation-induced catabolism, demonstrating anti-catabolic effects of ketone bodies in multifactorial atrophy.

Effects of Ketone Bodies on Endurance Exercise.

Priorities for every athlete include improving endurance performance, optimizing training, nutrition, and recovery. Nutritional strategies are crucial to support athletes to perform at the highest level, and considering that muscular and hepatic glycogen stores are limited, alternative strategies to maximize fat metabolism have been suggested. A ketogenic diet has been proposed as a possible method of providing metabolic fuel during prolonged periods of exercise. However, clinical trials and empirical experience have produced contrasting results regarding the ergogenic value of a ketogenic diet. For this reason, using ketone esters and/or salts have been proposed to obtain nutritional ketosis without limiting carbohydrate intake. Exogenous ketones should not only represent an alternative metabolic fuel source, sparing carbohydrates, but they also may increase postexercise glycogen replenishment, decrease proteolysis, and act as metabolic modulators and signaling metabolites. While there are some encouraging results showing an increase in endurance performance, contrasting evidence regarding the efficacy of exogenous ketones for endurance performance is present and further studies should be performed to make a definitive statement.

Decreased anxiety after Dawood fasting in the pre-elderly and elderly.

Background A high prevalence of anxiety in the elderly often leads to decreased quality of life (QOL). A restrictive diet can increase the production of ketone bodies that encourage mood enhancement, neural protection and pain reduction. This study aimed to identify whether Dawood fasting could increase the QOL of the elderly by reducing anxiety. Methods This research was a quasi-experimental study involving a pretest-post-test control group design. The subjects were pre-elderly and elderly or healthy people aged more than 50, and a consecutive sampling method was employed. The fasting group observed the fast of Dawood, in which they abstained from eating, drinking, or having sexual intercourse from the break of dawn to dusk with the expressed intent to fast every other day. The fast was observed for 22 days (11 fasting days). Anxiety was examined using the Hamilton Rating Scale for Anxiety (HRS-A), while QOL was identified using the Indonesian version of the World Health Organisation Quality of Life (WHOQOL). Results A total of 48 respondents participated in this study with 24 respondents observing the fast of Dawood and 24 others not fasting. Results showed that the 22 days of Dawood fast reduced respondents' complaints about anxiety by 4.37% and was significantly different from the non-fasting group (p=0.001). There was an increase in the QOL of the fasting group (p=0.019), although no significant difference was found when compared to the non-fasting group. Conclusions The fast of Dawood reduced anxiety in the pre-elderly and elderly.

Increases in circulating levels of ketone bodies and cardiovascular protection with SGLT2 inhibitors: Is low-grade inflammation the neglected component?

Recent clinical trials have demonstrated a strong cardiovascular (CV) protective effect of sodium/glucose cotransporter (SGLT) 2 inhibitors, a recently introduced class of hypoglycaemic agents. The improvement in glycated haemoglobin and other conventional risk factors explains only a portion of the observed reduction in CV risk. A relevant feature of SGLT2-inhibitor-treated diabetic patients is the increase in circulating levels of ketone bodies, which has been proposed to mediate part of the beneficial effects of this class of drugs, mainly through their bioenergetic properties. However, ketone bodies are emerging as potent anti-inflammatory molecules, and inflammation is a recognized risk factor for the development of CV events. In this framework, we hypothesize that, through their unique mechanism of action and by increasing circulating ketone bodies, SGLT2 inhibitors indirectly target the IL-1ß pathway and thus produce a consistent amelioration of low-grade inflammation, a clinically relevant phenomenon in diabetic patients with high CV risk. This attenuation could slow the progression of CV disease and especially the atherosclerotic process, which is sensitive to environmental changes, even over a short time period. To test this conceptual structure, it would be necessary to measure circulating pro-inflammatory molecules in patients treated with SGLT inhibitors. The addition of inflammatory markers to the list of clinical data measured in FDA-requested, large CV outcome trials could provide supplementary information regarding potential secondary effects of new anti-hyperglycaemic drugs, considering that the inflammatory process is an often neglected cornerstone of CV diseases.

The physiological stress response of the Atlantic stingray (Hypanus sabinus) to aerial exposure.

Although secondary stress physiology of elasmobranchs is fairly well studied, gaps remain in our understanding of species differences, including stress recovery. We examined the physiological stress response to air exposure in Atlantic stingrays (Hypanus sabinus) using a serial sampling method requiring minimal handling. Many elasmobranch stress studies exclusively quantify glucose, although there is evidence that elasmobranchs are unusually reliant on ketone bodies. Therefore, we also tested the hypothesis that ketone bodies play a significant role in the elasmobranch stress response by examining plasma ß-hydroxybutyrate. Plasma osmolality, urea, trimethylamine-N-oxide, and a suite of ions were also measured to characterize departures from homeostasis due to air exposure. H. sabinus were exposed to air for 30 min and serially sampled at 0, 15, and 30 min, as well as 48 h after the stressor to assess the extent of recovery. Blood lactate and acidosis increased significantly during the stressor and returned to basal levels by 48 h. Glucose values were significantly affected, with the highest values observed at 48 h, suggesting that animals were not fully recovered as initially indicated by other metrics. Average plasma ß-hydroxybutyrate was unaffected by the stressor. This suggests that ketone bodies may not be a major fuel source used during acute stress, at least in the timeframe examined.

Ketone bodies mimic the life span extending properties of caloric restriction.

The extension of life span by caloric restriction has been studied across species from yeast and Caenorhabditis elegans to primates. No generally accepted theory has been proposed to explain these observations. Here, we propose that the life span extension produced by caloric restriction can be duplicated by the metabolic changes induced by ketosis. From nematodes to mice, extension of life span results from decreased signaling through the insulin/insulin-like growth factor receptor signaling (IIS) pathway. Decreased IIS diminishes phosphatidylinositol (3,4,5) triphosphate (PIP3 ) production, leading to reduced PI3K and AKT kinase activity and decreased forkhead box O transcription factor (FOXO) phosphorylation, allowing FOXO proteins to remain in the nucleus. In the nucleus, FOXO proteins increase the transcription of genes encoding antioxidant enzymes, including superoxide dismutase 2, catalase, glutathione peroxidase, and hundreds of other genes. An effective method for combating free radical damage occurs through the metabolism of ketone bodies, ketosis being the characteristic physiological change brought about by caloric restriction from fruit flies to primates. A dietary ketone ester also decreases circulating glucose and insulin leading to decreased IIS. The ketone body, d-ß-hydroxybutyrate (d-ßHB), is a natural inhibitor of class I and IIa histone deacetylases that repress transcription of the FOXO3a gene. Therefore, ketosis results in transcription of the enzymes of the antioxidant pathways. In addition, the metabolism of ketone bodies results in a more negative redox potential of the NADP antioxidant system, which is a terminal destructor of oxygen free radicals. Addition of d-ßHB to cultures of C. elegans extends life span. We hypothesize that increasing the levels of ketone bodies will also extend the life span of humans and that calorie restriction extends life span at least in part through increasing the levels of ketone bodies. An exogenous ketone ester provides a new tool for mimicking the effects of caloric restriction that can be used in future research. The ability to power mitochondria in aged individuals that have limited ability to oxidize glucose metabolites due to pyruvate dehydrogenase inhibition suggests new lines of research for preventative measures and treatments for aging and aging-related disorders. © 2017 The Authors IUBMB Life published by Wiley Periodicals, Inc. on behalf of International Union of Biochemistry and Molecular Biology, 69(5):305-314, 2017.

How wasting is saving: weight loss at altitude might result from an evolutionary adaptation.

At extreme altitude (>5,000 - 5,500 m), sustained hypoxia threatens human function and survival, and is associated with marked involuntary weight loss (cachexia). This seems to be a coordinated response: appetite and protein synthesis are suppressed, and muscle catabolism promoted. We hypothesise that, rather than simply being pathophysiological dysregulation, this cachexia is protective. Ketone bodies, synthesised during relative starvation, protect tissues such as the brain from reduced oxygen availability by mechanisms including the reduced generation of reactive oxygen species, improved mitochondrial efficiency and activation of the ATP-sensitive potassium (KATP ) channel. Amino acids released from skeletal muscle also protect cells from hypoxia, and may interact synergistically with ketones to offer added protection. We thus propose that weight loss in hypoxia is an adaptive response: the amino acids and ketone bodies made available act not only as metabolic substrates, but as metabolic modulators, protecting cells from the hypoxic challenge.

Ketone body therapy: from the ketogenic diet to the oral administration of ketone ester.

Ketone bodies (KBs), acetoacetate and ß-hydroxybutyrate (ßHB), were considered harmful metabolic by-products when discovered in the mid-19th century in the urine of patients with diabetic ketoacidosis. It took physicians many years to realize that KBs are normal metabolites synthesized by the liver and exported into the systemic circulation to serve as an energy source for most extrahepatic tissues. Studies have shown that the brain (which normally uses glucose for energy) can readily utilize KBs as an alternative fuel. Even when there is diminished glucose utilization in cognition-critical brain areas, as may occur early in Alzheimer's disease (AD), there is preliminary evidence that these same areas remain capable of metabolizing KBs. Because the ketogenic diet (KD) is difficult to prepare and follow, and effectiveness of KB treatment in certain patients may be enhanced by raising plasma KB levels to ≥2 mM, KB esters, such as 1,3-butanediol monoester of ßHB and glyceryl-tris-3-hydroxybutyrate, have been devised. When administered orally in controlled dosages, these esters can produce plasma KB levels comparable to those achieved by the most rigorous KD, thus providing a safe, convenient, and versatile new approach to the study and potential treatment of a variety of diseases, including epilepsy, AD, and Parkinson's disease.

Short-chain fatty acids and ketones directly regulate sympathetic nervous system via G protein-coupled receptor 41 (GPR41).

The maintenance of energy homeostasis is essential for life, and its dysregulation leads to a variety of metabolic disorders. Under a fed condition, mammals use glucose as the main metabolic fuel, and short-chain fatty acids (SCFAs) produced by the colonic bacterial fermentation of dietary fiber also contribute a significant proportion of daily energy requirement. Under ketogenic conditions such as starvation and diabetes, ketone bodies produced in the liver from fatty acids are used as the main energy sources. To balance energy intake, dietary excess and starvation trigger an increase or a decrease in energy expenditure, respectively, by regulating the activity of the sympathetic nervous system (SNS). The regulation of metabolic homeostasis by glucose is well recognized; however, the roles of SCFAs and ketone bodies in maintaining energy balance remain unclear. Here, we show that SCFAs and ketone bodies directly regulate SNS activity via GPR41, a Gi/o protein-coupled receptor for SCFAs, at the level of the sympathetic ganglion. GPR41 was most abundantly expressed in sympathetic ganglia in mouse and humans. SCFA propionate promoted sympathetic outflow via GPR41. On the other hand, a ketone body, ß-hydroxybutyrate, produced during starvation or diabetes, suppressed SNS activity by antagonizing GPR41. Pharmacological and siRNA experiments indicated that GPR41-mediated activation of sympathetic neurons involves Gßγ-PLCß-MAPK signaling. Sympathetic regulation by SCFAs and ketone bodies correlated well with their respective effects on energy consumption. These findings establish that SCFAs and ketone bodies directly regulate GPR41-mediated SNS activity and thereby control body energy expenditure in maintaining metabolic homeostasis.

GABA depolarizes immature neocortical neurons in the presence of the ketone body ß-hydroxybutyrate.

A large body of evidence suggests that the neurotransmitter GABA undergoes a developmental switch from being predominantly depolarizing-excitatory to predominantly hyperpolarizing-inhibitory. Recently published data, however, point to the possibility that the presumed depolarizing mode of GABA action during early development might represent an artifact due to an insufficient energy supply of the in vitro preparations used. Specifically, addition of the ketone body dl-ß-hydroxybutyrate (ßHB) to the extracellular medium was shown to prevent GABA from exerting excitatory effects. Applying a complementary set of minimally invasive optical and electrophysiological techniques in brain slices from neonatal mice, we investigated the effects of ßHB on GABA actions in immature cells of the upper cortical plate. Fluorescence imaging revealed that GABA-mediated somatic [Ca(2+)] transients, that required activation of GABA(A) receptors and voltage-gated Ca(2+) channels, remained unaffected by ßHB. Cell-attached current-clamp recordings showed that, in the presence of ßHB, GABA still induced a membrane potential depolarization. To estimate membrane potential changes quantitatively, we used cell-attached recordings of voltage-gated potassium currents and demonstrated that the GABA-mediated depolarization was independent of supplementation of the extracellular solution with ßHB. We conclude that, in vitro, GABA depolarizes immature cells of the upper cortical plate in the presence of the ketone body ßHB. Our data thereby support the general concept of an excitatory-to-inhibitory switch of GABA action during early development.

Effects of ketone bodies on basal and insulin-stimulated glucose utilization in man.

Using the euglycemic clamp technique, we investigated the effects of high ketone body levels on basal and insulin-stimulated glucose utilization in normal subjects. Infusion of sodium acetoacetate in the postabsorptive state raised ketone body levels from 150 +/- 20 (+/- SE) mumol/liter to more than 1 mmol/liter. Endogenous glucose production declined from 2.71 +/- 0.20 mg kg-1 min-1 to 1.75 + 0.26 (P less than 0.01) and glucose utilization from 2.71 +/- 0.20 to 1.98 +/- 0.17 mg kg-1 min-1 (P less than 0.01), while blood glucose was maintained at the initial level by the infusion of glucose. There were no changes in plasma glucagon, insulin, or C-peptide. Plasma nonesterified fatty acids (P less than 0.01) and blood glycerol (P less than 0.01) and alanine (P less than 0.05) decreased, while blood lactate increased (P less than 0.01). Infusion of sodium bicarbonate had no effect on glucose kinetics. The decreases in glucose utilization and endogenous glucose production during the infusion of acetoacetate were not modified when the fall of plasma nonesterified fatty acids was prevented by iv heparin injection. During control euglycemic hyperinsulinemic clamps (1 and 10 mU kg-1 min-1 insulin infusion), endogenous glucose production was suppressed at the lowest insulin infusion rate; glucose utilization increased first to 7.32 +/- 0.96 mg kg-1 min-1 and then to 16.5 +/- 1.27 mg kg-1 min-1. During euglycemic hyperinsulinemic clamps with simultaneous sodium acetoacetate infusion, similar insulin levels were attained; endogenous glucose production was also suppressed at the lowest insulin infusion rate, and insulin-stimulated glucose utilization rates (7.93 +/- 1.70 and 15.80 +/- 1.30 mg kg-1 min-1) were not modified. In conclusion, acetoacetate infusion decreased basal, but not insulin-stimulated, glucose utilization. The increase in lactate during acetoacetate infusion in the postabsorptive state suggests that ketone body acted by decreasing pyruvate oxidation.

How important are carnitine and ketones for the newborn infant?

The newborn oxidizes a large amount of fat. This is reflected in the slow rise of plasma levels of ketones and of total carnitines and acylcarnitines. Feeding a diet devoid of carnitine (soy-based formulas, total parenteral nutrition [TPN] ) rapidly results in a fall in plasma total carnitine levels, whereas in the adult such a fall is observed only after a prolonged time of TPN. This suggests that carnitine synthesis in the newborn is less efficient than in the adult. Gluteal adipocytes in the newborn show a rise in carnitine content and in the activity of carnitine transferases soon after birth, when values are higher than in the adult. Their respiration, lipolysis, and triglyceride formation are enhanced by L-carnitine and inhibited by D-carnitine. This is not so in the adult. Addition of L-carnitine to soybean-based formulas decreases plasma triglyceride and free fatty acid levels in premature infants, who have lower carnitine levels at birth than full-term babies. In pregnant women plasma total carnitine levels are significantly depressed. maternal urinary excretion of total carnitine decreases as gestational age increases, and less is also found in amniotic fluid. Plasma levels of total carnitines and acylcarnitine are the same (or higher) in fetal as in maternal plasma. It is concluded that carnitine may be of particular importance to the neonate and that adding it to foods lacking this substance may be advantageous.

The hepato-muscular metabolic axis and gluconeogenesis.

During starvation alanine synthesised de novo by muscle is an important precursor for hepatic gluconeogenesis. The alanine carbon derives in part from branched-chain amino acids such as valine. In vitro incubations of muscle with [1-14 C]- or [U14C]-valine have shown that sufficient valine carbon passes beyond decarboxylation by branched-chain dehydrogenase, but escapes total oxidation, to account for the observed rate of de novo alanine synthesis. Experiments using hydroxymalonate (an inhibitor of malic enzyme) and mercaptopicolinate (an inhibitor of PEP carboxykinase) have shown that muscle alanine synthesis occurs via the latter route. Ketone bodies suppress muscle alanine formation suggesting a role in the conservation of glucogenic precursors in long-term starvation. Conversely alanine diminishes ketogenesis by isolated hepatocytes. It appears that there is an hepato-muscular metabolic axis operating by which liver and muscle metabolism is co-ordinately controlled by alanine and ketone bodies.