Identification of the toxic threshold of 3-hydroxybutyrate-sodium supplementation in septic mice

BACKGROUND

In septic mice, supplementing parenteral nutrition with 150 mg/day 3-hydroxybutyrate-sodium-salt (3HB-Na) has previously shown to prevent muscle weakness without obvious toxicity. The main objective of this study was to identify the toxic threshold of 3HB-Na supplementation in septic mice, prior to translation of this promising intervention to human use.

METHODS

In a centrally-catheterized, antibiotic-treated, fluid-resuscitated, parenterally fed mouse model of prolonged sepsis, we compared with placebo the effects of stepwise escalating doses starting from 150 mg/day 3HB-Na on illness severity and mortality (n = 103). For 5-day survivors, also the impact on ex-vivo-measured muscle force, blood electrolytes, and markers of vital organ inflammation/damage was documented.

RESULTS

By doubling the reference dose of 150 mg/day to 300 mg/day 3HB-Na, illness severity scores doubled (p = 0.004) and mortality increased from 30.4 to 87.5 % (p = 0.002). De-escalating this dose to 225 mg still increased mortality (p ≤ 0.03) and reducing the dose to 180 mg/day still increased illness severity (p ≤ 0.04). Doses of 180 mg/day and higher caused more pronounced metabolic alkalosis and hypernatremia (p ≤ 0.04) and increased markers of kidney damage (p ≤ 0.05). Doses of 225 mg/day 3HB-Na and higher caused dehydration of brain and lungs (p ≤ 0.05) and increased markers of hippocampal neuronal damage and inflammation (p ≤ 0.02). Among survivors, 150 mg/day and 180 mg/day increased muscle force compared with placebo (p ≤ 0.05) up to healthy control levels (p ≥ 0.3).

CONCLUSIONS

This study indicates that 150 mg/day 3HB-Na supplementation prevented sepsis-induced muscle weakness in mice. However, this dose appeared maximally effective though close to the toxic threshold, possibly in part explained by excessive Na+ intake with 3HB-Na. Although lower doses were not tested and thus might still hold therapeutic potential, the current results point towards a low toxic threshold for the clinical use of ketone salts in human critically ill patients. Whether 3HB-esters are equally effective and less toxic should be investigated.

Enantiomer-specific pharmacokinetics of D,L-3-hydroxybutyrate: Implications for the treatment of multiple acyl-CoA dehydrogenase deficiency

D,L-3-hydroxybutyrate (D,L-3-HB, a ketone body) treatment has been described in several inborn errors of metabolism, including multiple acyl-CoA dehydrogenase deficiency (MADD; glutaric aciduria type II). We aimed to improve the understanding of enantiomer-specific pharmacokinetics of D,L-3-HB. Using UPLC-MS/MS, we analyzed D-3-HB and L-3-HB concentrations in blood samples from three MADD patients, and blood and tissue samples from healthy rats, upon D,L-3-HB salt administration (patients: 736-1123 mg/kg/day; rats: 1579-6317 mg/kg/day of salt-free D,L-3-HB). D,L-3-HB administration caused substantially higher L-3-HB concentrations than D-3-HB. In MADD patients, both enantiomers peaked at 30 to 60 minutes, and approached baseline after 3 hours. In rats, D,L-3-HB administration significantly increased C_max and AUC of D-3-HB in a dose-dependent manner (controls vs ascending dose groups for C_max : 0.10 vs 0.30-0.35-0.50 mmol/L, and AUC: 14 vs 58-71-106 minutes*mmol/L), whereas for L-3-HB the increases were significant compared to controls, but not dose proportional (C_max : 0.01 vs 1.88-1.92-1.98 mmol/L, and AUC: 1 vs 380-454-479 minutes*mmol/L). L-3-HB concentrations increased extensively in brain, heart, liver, and muscle, whereas the most profound rise in D-3-HB was observed in heart and liver. Our study provides important knowledge on the absorption and distribution upon oral D,L-3-HB. The enantiomer-specific pharmacokinetics implies differential metabolic fates of D-3-HB and L-3-HB.

14-Day Ketone Supplementation Lowers Glucose and Improves Vascular Function in Obesity: A Randomized Crossover Trial

CONTEXT

Postprandial hyperglycemia increases systemic inflammation and is a risk factor for cardiovascular disease. A ketone monoester (KME) drink containing β-hydroxybutyrate (β-OHB) rapidly lowers plasma glucose, which may be a strategy protecting against postprandial hyperglycemia.

OBJECTIVE

We hypothesized that KME would attenuate 2-hour postprandial glucose, lower systemic inflammation, and improve vascular function in adults with obesity.

METHODS

In a randomized crossover design, 14 participants with obesity (age = 56 ± 12 years; body mass index = 32.8 ± 7.7 kg/m2) consumed KME (12 g β-OHB) or placebo 15 minutes prior to each meal for 14 days with all meals provided and matched between conditions. Postprandial glycemia was assessed by continuous glucose monitoring. Vascular function and inflammation were assessed before and after treatment periods.

RESULTS

Postprandial glucose was 8.0% lower in KME versus placebo (g = 0.735; P = 0.011) and 24-hour average glucose reduced by 7.8% (g = 0.686; P = 0.0001). Brachial artery flow-mediated dilation increased from 6.2  ±  1.5% to 8.9 ± 3.3% in KME (g = 1.05; P = 0.0004) with no changes in placebo (condition × time interaction, P = 0.004). There were no changes in plasma cytokines; however, lipopolysaccharide-stimulated monocyte caspase-1 activation was lower following KME supplementation versus placebo (stimulation × condition × time interaction; P = 0.004). The KME supplement was well tolerated by participants and adherence to the supplementation regimen was very high.

CONCLUSIONS

In adults with obesity, 14 days of premeal KME supplementation improves glucose control, enhances vascular function, and may reduce cellular inflammation. KME supplementation may be a viable, nonpharmacological approach to improving and protecting vascular health in people with heightened cardiometabolic risk.

The Effect of Exogenous Beta-Hydroxybutyrate Salt Supplementation on Metrics of Safety and Health in Adolescents

The ketogenic diet is a high-fat, very low-carbohydrate, moderate-protein diet that will induce a state of ketosis, but because of its restrictive nature, it may be difficult to adhere to, especially in adolescents. Supplementing with exogenous beta-hydroxybutyrate salts may induce a state of temporary ketosis without any undesirable side effects, thereby promoting the benefits of ketosis and minimizing adherence requirements to a ketogenic diet. To date, beta-hydroxybutyrate supplementation in healthy adolescents has not been explored. Therefore, the purpose of this study was to examine the safety of exogenous beta-hydroxybutyrate salt supplementation in a healthy adolescent population. In the present study, 22 healthy male and female adolescents consumed 3.75 g of beta-hydroxybutyrate salts or maltodextrin placebo twice daily for 90 days. Comprehensive blood safety analysis, bone densitometry, happiness and emotional intelligence surveys, and blood pressure were assessed at Pre, Day 45, and Day 90. There were no significant differences detected in subjects supplementing with beta-hydroxybutyrate salts, indicating that exogenous beta-hydroxybutyrate salts had no detrimental impact on fasting blood safety metrics, bone density, happiness, emotional intelligence, or blood pressure. We conclude that supplementing with exogenous beta-hydroxybutyrate salts is safe and well-tolerated by healthy adolescents.

The Effect of Blood Ketone Concentration and Exercise Intensity on Exogenous Ketone Oxidation Rates in Athletes

INTRODUCTION

Exogenous ketones potentially provide an alternative, energetically advantageous fuel to power exercising skeletal muscle. However, there is limited evidence regarding their relative contribution to energy expenditure during exercise. Furthermore, the effect of blood ketone concentration and exercise intensity on exogenous ketone oxidation rates is unknown.

METHODS

Six athletes completed cycling ergometer exercise on three occasions within a single-blind, random-order controlled, crossover design study. Exercise duration was 60 min, consisting of 20-min intervals at 25%, 50%, and 75% maximal power output (WMax). Participants consumed (i) bitter flavored water (control), (ii) a low-dose β-hydroxybutyrate (βHB) ketone monoester (KME; 252 mg·kg BW-1, "low ketosis"), or (iii) a high-dose βHB KME (752 mg·kg BW-1, "high ketosis"). The KME contained a 13C isotope label, allowing for the determination of whole-body exogenous βHB oxidation rates through sampled respiratory gases.

RESULTS

Despite an approximate doubling of blood βHB concentrations between low- and high-ketosis conditions (~2 mM vs ~4.4 mM), exogenous βHB oxidation rates were similar at rest and throughout exercise. The contribution of exogenous βHB oxidation to energy expenditure peaked during the 25% WMax exercise intensity but was relatively low (4.46% ± 2.71%). Delta efficiency during cycling exercise was significantly greater in the low-ketosis (25.9% ± 2.1%) versus control condition (24.1% ± 1.9%; P = 0.027).

CONCLUSIONS

Regardless of exercise intensity, exogenous βHB oxidation contributes minimally to energy expenditure and is not increased by elevating circulating concentrations greater than ~2 mM. Despite low exogenous βHB oxidation rates, exercise efficiency was significantly improved when blood βHB concentration was raised to ~2 mM.

Impact of Acutely Increased Endogenous- and Exogenous Ketone Bodies on FGF21 Levels in Humans

PURPOSE

Fibroblast growth factor (FGF) 21 is a circulating hormone with metabolic regulatory importance. In mice, FGF21 increases in response to a ketogenic diet and fasting. In humans, a similar increase is only observed after prolonged starvation. We aim to study the acute effects of ketone bodies on circulating FGF21 levels in humans.

METHODS

Participants from three randomized, placebo-controlled crossover studies, with increased endogenous or exogenous ketone bodies, were included. Study 1: patients with type 1 diabetes (T1D) (n = 9) were investigated after a) insulin deprivation and lipopolysaccharide (LPS) injection and b) insulin-controlled euglycemia. Study 2: patients with T1D (n = 9) were investigated after a) total insulin deprivation for 9 hours and b) insulin-controlled euglycemia. Study 3: Healthy adults (n = 9) were examined during a) 3-hydroxybutyrate (OHB) infusion and b) saline infusion. Plasma FGF21 was measured with immunoassay in serial samples.

RESULTS

Circulating OHB levels were significantly increased to 1.3, 1.5, and 5.5 mmol/l in the three studies, but no correlations with FGF21 levels were found. Also, no correlations between FGF21, insulin, or glucagon were found. Insulin deprivation and LPS injection resulted in increased plasma FGF21 levels at t = 120 min (p = .005) which normalized at t = 240 min.

CONCLUSION

We found no correlation between circulating FGF21 levels and levels of ketone bodies. This suggests that it is not ketosis per se which controls FGF21 production, but instead a rather more complex regulatory mechanism.

TRIAL REGISTRATION

clinicaltrials.gov ID number: Study 1: NCT02157155 (5/6-2014), study 2: NCT02077348 (4/3-2014), and study 3: NCT02357550 (6/2-2015).

Oral D/L-3-Hydroxybutyrate Stimulates Cholecystokinin and Insulin Secretion and Slows Gastric Emptying in Healthy Males

BACKGROUND

D-3-hydroxybutyrate (D-3-OHB) is a ketone body that serves as an alternative nutritional fuel but also as an important signaling metabolite. Oral ketone supplements containing D/L-3-OHB are becoming a popular approach to achieve ketosis.

AIM

To explore the gut-derived effects of ketone supplements.

METHODS

Eight healthy lean male volunteers were investigated on 2 separate occasions:An acetaminophen test was performed to evaluate gastric emptying and blood samples were obtained consecutively throughout the study period.

RESULTS

We show that oral consumption of D/L-3-OHB stimulates cholecystokinin release (P = 0.02), elevates insulin (P = 0.03) and C-peptide (P < 0.001) concentrations, and slows gastric emptying (P = 0.01) compared with matched intravenous D/L-3-OHB administration. Measures of appetite and plasma concentrations of glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) were unaffected by interventions.

CONCLUSION

Our findings show that D/L-3-OHB exert incretin effects and indicate luminal sensing in the gut endothelium. This adds to our understanding of ketones as signaling metabolites and displays the important difference between physiological ketosis and oral ketone supplements.

The Impact of Acute Ingestion of a Ketone Monoester Drink on LPS-Stimulated NLRP3 Activation in Humans with Obesity

Activation of the NOD-like receptor pyrin-domain containing 3 (NLRP3) inflammasome is associated with chronic low-grade inflammation in metabolic diseases such as obesity. Mechanistic studies have shown that β-hydroxybutyrate (OHB) attenuates activation of NLRP3, but human data are limited. In a randomized, double-blind, placebo-controlled crossover trial (n = 11) we tested the hypothesis that acutely raising β-OHB by ingestion of exogenous ketones would attenuate NLRP3 activation in humans with obesity. Blood was sampled before and 30 min post-ingestion of a ketone monoester drink ((R)-3-hydroxybutyl (R)-3-hydroxybutyrate, 482 mg/kg body mass) or placebo. A 75 g oral glucose load was then ingested, and a third blood sample was obtained 60 min following glucose ingestion. NLRP3 activation was quantified by assessing monocyte caspase-1 activation and interleukin (IL)-1β secretion in ex vivo lipopolysaccharide (LPS)-stimulated whole-blood cultures. LPS-stimulated caspase-1 activation increased following glucose ingestion (main effect of time; p = 0.032), with no differences between conditions. IL-1β secretion did not differ between conditions but was lower 60 min post-glucose ingestion compared to the fasting baseline (main effect of time, p = 0.014). Plasma IL-1β was detectable in ~80% of samples and showed a decrease from fasting baseline to 60 min in the ketone condition only (condition × time interaction, p = 0.01). In individuals with obesity, an excursion into hyperglycemia following ingestion of a glucose load augments LPS-induced activation of caspase-1 in monocytes with no apparent impact of raising circulating β-OHB concentration via ingestion of exogenous ketones. Exogenous ketone supplementation may impact plasma IL-1β, but these findings require confirmation in studies with larger sample sizes.

β-hydroxybutyrate antagonizes aortic endothelial injury by promoting generation of VEGF in diabetic rats

Endothelial injury is regarded as the initial pathological process in diabetic vascular diseases, but effective therapy has not yet been identified. Although β-hydroxybutyrate plays various protective roles in the cardiovascular system, its ability to antagonize diabetic endothelial injury is unclear. β-hydroxybutyrate reportedly causes histone H3K9 β-hydroxybutyrylation (H3K9bhb), which activates gene expression; however, there has been no report regarding the role of H3K9bhb in up-regulation of vascular endothelial growth factor (VEGF), a crucial factor in endothelial integrity and function. Here, male Sprague-Dawley rats were intraperitoneally injected with streptozotocin to induce diabetes, and then treated with different concentrations of β-hydroxybutyrate. After 10 weeks, body weight, blood glucose, morphological changes and serum nitric oxide concentration were examined. Moreover, the mRNA expression level, protein content and distribution of VEGF in the aorta were investigated, as were total protein β-hydroxybutyrylation and H3K9bhb contents. The results showed injury of aortic endothelium, along with reductions of the concentration of nitric oxide and generation of VEGF in diabetic rats. However, β-hydroxybutyrate treatment attenuated diabetic injury of the endothelium and up-regulated the generation of VEGF. Furthermore, β-hydroxybutyrate treatment caused marked total protein β-hydroxybutyrylation and significant elevation of H3K9bhb content in the aorta of diabetic rats. The ability of β-hydroxybutyrate to protect against diabetic injury of the aortic endothelium was greatest for its intermediate concentration. In conclusion, moderately elevated β-hydroxybutyrate could antagonize aortic endothelial injury, potentially by causing H3K9bhb to promote generation of VEGF in diabetic rats.

Regional cerebral effects of ketone body infusion with 3-hydroxybutyrate in humans: Reduced glucose uptake, unchanged oxygen consumption and increased blood flow by positron emission tomography. A randomized, controlled trial

Ketone bodies are neuroprotective in neurological disorders such as epilepsy. We randomly studied nine healthy human subjects twice—with and without continuous infusion of 3-hydroxybutyrate–to define potential underlying mechanisms, assessed regionally (parietal, occipital, temporal, cortical grey, and frontal) by PET scan. During 3-hydroxybutyrate infusions concentrations increased to 5.5±0.4 mmol/l and cerebral glucose utilisation decreased 14%, oxygen consumption remained unchanged, and cerebral blood flow increased 30%. We conclude that acute 3-hydroxybutyrate infusion reduces cerebral glucose uptake and increases cerebral blood flow in all measured brain regions, without detectable effects on cerebral oxygen uptake though oxygen extraction decreased. Increased oxygen supply concomitant with unchanged oxygen utilisation may contribute to the neuroprotective effects of ketone bodies.

D-β-Hydroxybutyrate and melatonin for treatment of porcine hemorrhagic shock and injury: a melatonin dose-ranging study

OBJECTIVE

Treatment with a combination of D-β-hydroxybutyrate (BHB) and melatonin (M) improves survival in hemorrhagic shock models. Our objective was to find the most effective melatonin concentration in combination with 4 molar BHB (4 M BHB). Survival and markers of organ injury were analyzed in pigs exposed to pulmonary contusion, liver crush injury, and hemorrhagic shock and treated with lactated Ringer's solution; 4 M BHB/43 mM M; 4 M BHB/20 mM M; 4 M BHB/10 mM M; 4 M BHB/4.3 mM M; or 4 M BHB/0.43 mM M. This work is an extension of a previously published research study.

RESULTS

Survival was highest in pigs receiving 4 M BHB/43 mM M (13/14), followed by lactated Ringer's solution (11/16) and BHB/M with decreased melatonin concentrations (4 M BHB/20 mM M 3/6, 4 M BHB/10 mM M 2/6, 4 M BHB/4.3 mM M 3/6, 4 M BHB/0.43 mM M 1/6, p = 0.011). High mortality was associated with increases in serum lactate, higher liver and muscle injury markers and decreases in PaO2:FiO2 ratios. Our study indicates that treatment with 4 M BHB and melatonin concentrations below 43 mM lack the survival benefit observed from 4 M BHB/43 mM melatonin in pigs experiencing hemorrhagic shock and polytrauma.

The extracellular redox state modulates mitochondrial function, gluconeogenesis, and glycogen synthesis in murine hepatocytes

Circulating redox state changes, determined by the ratio of reduced/oxidized pairs of different metabolites, have been associated with metabolic diseases. However, the pathogenic contribution of these changes and whether they modulate normal tissue function is unclear. As alterations in hepatic gluconeogenesis and glycogen metabolism are hallmarks that characterize insulin resistance and type 2 diabetes, we tested whether imposed changes in the extracellular redox state could modulate these processes. Thus, primary hepatocytes were treated with different ratios of the following physiological extracellular redox couples: β-hydroxybutyrate (βOHB)/acetoacetate (Acoc), reduced glutathione (GSH)/oxidized glutathione (GSSG), and cysteine/cystine. Exposure to a more oxidized ratio via extracellular βOHB/Acoc, GSH/GSSG, and cysteine/cystine in hepatocytes from fed mice increased intracellular hydrogen peroxide without causing oxidative damage. On the other hand, addition of more reduced ratios of extracellular βOHB/Acoc led to increased NAD(P)H and maximal mitochondrial respiratory capacity in hepatocytes. Greater βOHB/Acoc ratios were also associated with decreased β-oxidation, as expected with enhanced lipogenesis. In hepatocytes from fasted mice, a more extracellular reduced state of βOHB/Acoc led to increased alanine-stimulated gluconeogenesis and enhanced glycogen synthesis capacity from added glucose. Thus, we demonstrated for the first time that the extracellular redox state regulates the major metabolic functions of the liver and involves changes in intracellular NADH, hydrogen peroxide, and mitochondrial respiration. Because redox state in the blood can be communicated to all metabolically sensitive tissues, this work confirms the hypothesis that circulating redox state may be an important regulator of whole body metabolism and contribute to alterations associated with metabolic diseases.

Twin-pregnancy increases susceptibility of ewes to hypoglycaemic stress and pregnancy toxaemia

Pregnancy toxaemia is a metabolic disorder with a high mortality rate and occurs in twin-bearing ewes in late gestation. Maternal hypoglycaemia is a characteristic symptom of the disease and has been attributed to an increase in glucose uptake by the twin-bearing uterus. The possibility that a reduced maternal glucose production rate might cause hypoglycaemia, has received little attention in the past. It was the aim of this study to investigate this explanation as a possible alternative. Six ewes were sequentially subjected to two types of hypoglycaemic stress, firstly by fasting for 14 h and secondly through induction of moderate hyperketonaemia. Glucose kinetics were assessed in each animal during the dry non-gestational period, during late gestation, and during early lactation. Application of these stress factors was associated with variation of plasma glucose concentration from 4.9 to 0.87 mmol L(-1). The plasma glucose concentration was always significantly related to the glucose production rate. The greatest stress-induced reductions in glucose concentration and glucose production rate were seen during late gestation in twin-bearing ewes. The decline in the glucose production rate after an overnight fast and during induced hyperketonaemia was greater in twin-bearing ewes than in single-bearing ewes (59% and 43%, respectively, p<0.05). The stress conditions resulted in the lowest levels of glucose concentration and glucose turnover rates in the stressed, hyperketonaemic, late gestation twin-bearing ewes. This illustrates that the glucose homoeostatic system of ewes bearing twins is significantly more susceptible to hypoglycaemic stress than that of ewes bearing single lambs. These findings also show that the primary cause of hypoglycaemia in late gestation twin-pregnant ewes is an increased susceptibility to a stress related reduction in glucose production rate. This metabolic condition leaves the twin-pregnant ewe predisposed for the development of pregnancy toxaemia.

β-Hydoxy-β-methylbutyrate supplementation affects Walker 256 tumor-bearing rats in a time-dependent manner

BACKGROUND & AIMS

Cancer cachexia affects intermediary metabolism with intense and general catabolism. Walker 256 tumor is a model injected either subcutaneously (Sc) or intraperitoneally (Ip), with different metabolic features. Beta-hydroxy beta-methylbutyrate (HMbeta) is a leucine metabolite with anti-catabolic properties, the aim of this study being to investigate its effects on metabolic parameters in both tumor models.

METHODS

Controls (subcutaneous control group (ScC) and intraperitoneal control group (IpC)) and supplemented animals (subcutaneous supplemented group (ScS) and intraperitoneal supplemented group (IpS)) showed these results.

RESULTS

Protein Sc values were (47.8%) lower than Ip groups. Sc group fat content was (65.16%) higher than Ip groups. Liver glycogen value for Sc groups was (38.4%) higher than Ip groups. Muscle glycogen value for Sc groups were (2.75 times) higher than Ip groups. Corticosterone and insulin values were lower (44.53%) and higher (45.94%), respectively, in Sc when compared with Ip groups. Glucose and lactate values for ScS were the lowest (61.7% and 41.53%) compared to other groups. ScC glutamine value was the highest (40.8%) of all groups. Glutamate Sc values were (42.65%) lower than Ip groups. Sc groups showed greater survival time compared with Ip groups. ScS group showed 100% increase in survival time when compared with ScC.

CONCLUSIONS

HMbeta supplementation can increase survival time and promotes metabolic changes in cancer-bearing animals, but it seems to work in a time-dependent manner.

Global cerebral blood flow and metabolism during acute hyperketonemia in the awake and anesthetized rat

In the human setting, it has been shown that acute increase in the concentration of ketone bodies by infusion of beta-hydroxybutyrate increased the cerebral blood flow (CBF) without affecting the overall cerebral metabolic activity. The mechanism by which this effect of ketone bodies was mediated is not known. Alterations in several parameters may possibly explain the increase in CBF and the resetting of the relation between CBF and cerebral metabolism. To study this phenomenon further, we measured global CBF and global cerebral metabolism with the Kety-Schmidt technique in the wakeful rat before and during infusion of ketone bodies. During acute hyperketonemia (average concentration of beta-hydroxybutyrate: 6 mmol/L), global CBF increased 65% from 108 to 178 mL/100 g min and the cerebral metabolic rates for both oxygen and glucose remained constant. This resetting of the relation between CBF and cerebral metabolism could not be explained by alterations in blood pH or arterial CO2 tension. By measuring cerebral intracellular pH by 31P nuclear magnetic resonance spectroscopy, it could further be concluded that the brain pH was unchanged during acute hyperketonemia. These observations indicate that the mechanism responsible for the increase in CBF is rather a direct effect on the cerebral endothelium than via some metabolic interactions.

Supplementation with a combination of beta-hydroxy-beta-methylbutyrate (HMB), arginine, and glutamine is safe and could improve hematological parameters

BACKGROUND

Combining the amino acids arginine and glutamine with the leucine metabolite beta-hydroxy-beta-methylbutyrate (HMB) has been shown to reverse lean tissue loss in cancer and acquired immunodeficiency syndrome (AIDS) patients. Although each of these nutrients has been shown to be safe, the safety of this mixture has not been reported. Three double-blind studies examined the safety of the combination of HMB, arginine and glutamine on blood chemistries, hematology, emotional profile, and adverse events.

METHODS

Study 1 was conducted in healthy adult males (n = 34), study 2 was in HIV patients with AIDS-associated weight loss (n = 43), and study 3 was in cancer patients with wasting (n = 32). Volunteers were assigned to either a placebo or a mixture of 3 g HMB, 14 g arginine, and 14 g glutamine per day.

RESULTS

Across the 3 studies, HMB, arginine, and glutamine supplementation was not associated with any adverse indicators of health. The only significant changes noted were positive indicators of health status. HMB, arginine, and glutamine supplementation was associated with an improvement in emotional profile (p = .05), a decreased feeling of weakness (p = .03), and increased red blood cells, hemoglobin, hematocrit, lymphocytes, and eosinophils (p < .05) when compared with placebo-supplemented subjects. Blood creatinine levels were not changed. However, blood urea nitrogen increased (p = .01) with HMB, arginine, and glutamine supplementation, which was possibly caused by the additional nitrogen consumed or to the fact that ureagenesis is influenced by arginine and glutamine supplementation.

CONCLUSION

These results show that HMB, arginine, and glutamine can be safely used to treat muscle wasting associated with AIDS and cancer.

Hyperketonemia Impairs Glucose Metabolism in Pregnant and Nonpregnant Ewes

The present study was undertaken to test the hypothesis that high ketone body concentrations suppress endogenous production of glucose and in pregnant sheep facilitate development of pregnancy toxemia. Rates of endogenous glucose production [mmol.min(-1)], and rate constants of glucose turnover [min(-1)] were measured in seven 12-h fasted sheep in the presence of normo- and hyperketonemia by use of D-2-[(3)H]-glucose. The measurements were carried out in the same sheep during the nonpregnant nonlactating state, during late pregnancy (10 +/- 7 d antepartum) and during lactation (19 +/- 6 d postpartum). Hyperketonemia (5 to 7 mmol.L(-1)), similar to that present in spontaneous ovine pregnancy toxemia, was induced by continuous intravenous 4-h infusions of DL-beta-hydroxybutyrate (DL-BHB). Glucose turnover [mmol.min(-1)] in the same 7 nonpregnant nonlactating, late pregnant, and lactating sheep was significantly greater during normoketonemia (0.80, 1.16, 1.76) than during hyperketonemia (0.66, 0.92, 1.16, respectively). The rate constants of glucose turnover were not altered by elevation of the BHB concentration. The results demonstrated that high BHB concentrations significantly suppressed endogenous glucose production but showed no effect on glucose utilization. The suppressive effect of hyperketonemia on hepatic glucose production resulted in a significant reduction of plasma glucose concentration and was qualitatively the same in all three reproductive states. The results indicate that hyperketonemia, which is regularly present in late twin pregnant hypoglycemic sheep contributes significantly to the reduction of available glucose. This effect of hyperketonemia may invoke sustained hypoglycemia and may render the ewe into a vicious cycle that probably makes the animal refractory to treatment in most cases.

Protective effect of D-beta-hydroxybutyrate on corneal epithelia in dry eye conditions through suppression of apoptosis

PURPOSE

To investigate the effect of D-beta-hydroxybutyrate (HBA) on ocular surface epithelial disorders induced by tear fluid deficiency, the potency of HBA and serum, the efficacy of which has been well documented in clinical application, were compared.

METHODS

Rat corneal epithelial erosion was induced by exposure of rat eyes to continuous low-humidity airflow, which accelerated the tear evaporation. During desiccation, one eye of each rat was treated with HBA (20, 40, or 80 mM) or rat serum (5%, 20%, or 100%), and in the other eye a drop of phosphate-buffered saline (PBS) was instilled as the control. Histopathologic examination and quantification of the epithelial defect area were performed. The apoptosis in the epithelia was determined by chromatin condensation using the Hoechst 33342 fluorescein probe.

RESULTS

In PBS-treated eyes, thinning in the cell layer was seen on the periphery of the initial wound after 6 hours, and it progressed to defects after 12 hours. In the 80-mM HBA and 20% serum applications, the pathologic change in the epithelia was moderate, and the structure was maintained in an almost normal state in the 100% serum application. Significant decreases in the defect areas were observed in the 5%, 20%, and 100% serum and 40- and 80-mM HBA treatment groups compared with the PBS-treated eyes (n=12). A significant suppression of chromatin condensation was observed with HBA and serum treatment.

CONCLUSIONS

These results suggest the potential clinical application of HBA for ocular surface epithelial disorders to maintain epithelial cell viability in patients with dry eye.

Ketone and pyruvate Ringer's solutions decrease pulmonary apoptosis in a rat model of severe hemorrhagic shock and resuscitation

BACKGROUND

Resuscitation fluids containing beta-hydroxybutyrate (BHB) have been shown to decrease cellular injury after hemorrhagic shock and resuscitation through an unknown mechanism. We tested whether this effect was related to BHB-induced metabolic modulations.

METHODS

Male Sprague Dawley rats (n=30) were subjected to volume-controlled hemorrhage (27 mL/kg during 10 minutes followed by 75 minutes of shock during which another 8 mL/kg of blood was withdrawn). Experimental groups included the following: (1) sham, (2) no resuscitation (NR), (3) racemic lactated Ringer's (DL-LR) solution, (4) LR containing L-isomer only (L-LR), (5) ketone Ringer's solution with lactate substituted by BHB (KR), and (6) pyruvate Ringer's solution with lactate substituted by pyruvate (PR). The resuscitation fluids were infused during 45 minutes simultaneously with additional hemorrhage of 8 mL/kg. Hemodynamic and physiologic parameters and the plasma levels of BHB were serially measured. The animals were killed 2 hours after resuscitation, and tissues were frozen instantaneously for cellular adenylate extraction and adenosine triphosphate (ATP) and adenosine diphosphate analysis. Pulmonary apoptosis was studied using Western blotting, immunohistochemistry, and reverse transcriptase-polymerase chain reaction. Expression of enzymes involved in ketogenesis and ketolysis was analyzed by reverse transcriptase-polymerase chain reaction.

RESULTS

NR and resuscitation with DL-LR increased the expression of apoptotic markers, whereas resuscitation with KR and PR significantly decreased the expression of apoptotic markers in rat lungs. Resuscitation with KR was followed by a profound increase in plasma BHB levels; however, the expression levels of ketolytic enzymes were essentially unaffected. KR infusion did not induce significant improvements in tissue ATP levels.

CONCLUSIONS

Resuscitation with KR and PR protects against pulmonary apoptosis without improving tissue ATP content. Therefore, metabolic modulation is unlikely to be the major mechanism by which BHB exerts its protective effects during reperfusion.

Acetoacetate increases expression of intercellular adhesion molecule-1 (ICAM-1) in human brain microvascular endothelial cells

It has been hypothesized that ketone bodies cause activation of brain endothelial cells and that this is a factor in the intracerebral crises of diabetic ketoacidosis (DKA). In this study we used cultured human brain microvascular endothelial cells (HBMEC) to investigate the effect of beta hydroxybutyrate (BOHB) and acetoacetate (AcAc) on the expression of the adhesion molecule, intercellular adhesion molecule-1 (ICAM-1). Increasing concentrations of AcAc, but not BOHB, caused a significant upregulation of ICAM-1 in comparison to unstimulated cells. Glucose concentrations of 10 and 30 mM, but not 50 mM, also resulted in increased expression of ICAM-1. These results support the hypothesis that activation of HBMEC is involved in the acute complications of DKA, and that ketone bodies and hyperglycemia are factors in the perturbed membrane function.

Oral beta-hydroxybutyrate supplementation in two patients with hyperinsulinemic hypoglycemia: monitoring of beta-hydroxybutyrate levels in blood and cerebrospinal fluid, and in the brain by in vivo magnetic resonance spectroscopy

In persistent hyperinsulinemic hypoglycemia of infancy, ketone body concentrations are abnormally low at times of hypoglycemia, depriving the brain of its most important alternative fuel. The neuroprotective effect of endogenous ketone bodies is evidenced by animal and human studies, but knowledge about exogenous supply is limited. Assuming that exogenous ketone body compounds as a dietetic food might replace this alternative energy source for the brain, we have monitored the fate of orally supplemented DL sodium beta-hydroxybutyrate (beta-OHB) in two 6-mo-old infants with persistent hyperinsulinemic hypoglycemia for 5 and 7 mo, while on frequent tube-feedings and treatment with octreotide. Near total (95%) pancreatectomy had been ineffective in one patient and was refused in the other. In blood, concentrations of beta-OHB increased to levels comparable to a 16- to 24-h fast while on DL sodium beta-OHB 880 to 1000 mg/kg per day. In cerebrospinal fluid, concentrations of beta-OHB increased to levels comparable to a 24- to 40-h fast, after single dosages of 4 and 8 g, respectively. High ratios of beta-OHB to acetoacetate indicated exogenous origin of beta-OHB. An increase of intracerebral concentrations of beta-OHB could be demonstrated by repetitive single-voxel proton magnetic resonance spectroscopy by a clear doublet at 1.25 ppm. Oral DL sodium beta-OHB was tolerated without side effects. This first report on oral supplementation of DL sodium beta-OHB in two patients with persistent hyperinsulinemic hypoglycemia demonstrates effective uptake across the blood-brain barrier and could provide the basis for further evaluation of the neuroprotective effect of beta-OHB in conditions with hypoketotic hypoglycemia.

Effect of acute hyperketonemia on the cerebral uptake of ketone bodies in nondiabetic subjects and IDDM patients

Using R-beta-[1-(11)C]hydroxybutyrate and positron emission tomography, we studied the effect of acute hyperketonemia (range 0.7-1.7 micromol/ml) on cerebral ketone body utilization in six nondiabetic subjects and six insulin-dependent diabetes mellitus (IDDM) patients with average metabolic control (HbA(1c) = 8.1 +/- 1.7%). An infusion of unlabeled R-beta-hydroxybutyrate was started 1 h before the bolus injection of R-beta-[1-(11)C]hydroxybutyrate. The time course of the radioactivity in the brain was measured during 10 min. For both groups, the utilization rate of ketone bodies was found to increase nearly proportionally with the plasma concentration of ketone bodies (1.0 +/- 0.3 micromol/ml for nondiabetic subjects and 1.3 +/- 0.3 micromol/ml for IDDM patients). No transport of ketone bodies from the brain could be detected. This result, together with a recent study of the tissue concentration of R-beta-hydroxybutyrate in the brain by magnetic resonance spectroscopy, indicate that, also at acute hyperketonemia, the rate-limiting step for ketone body utilization is the transport into the brain. No significant difference in transport and utilization of ketone bodies could be detected between the nondiabetic subjects and the IDDM patients.

[2,4-13 C2 ]-beta-Hydroxybutyrate metabolism in human brain

Infusions of [2,4-13C2]-beta-hydroxybutyrate and 1H-13C polarization transfer spectroscopy were used in normal human subjects to detect the entry and metabolism of beta-hydroxybutyrate in the brain. During the 2-hour infusion study, 13C label was detectable in the beta-hydroxybutyrate resonance positions and in the amino acid pools of glutamate, glutamine, and aspartate. With a plasma concentration of 2.25 +/- 0.24 mmol/L (four volunteers), the apparent tissue beta-hydroxybutyrate concentration reached 0.18 +/- 0.06 mmol/L during the last 20 minutes of the study. The relative fractional enrichment of 13C-4-glutamate labeling was 6.78 +/- 1.71%, whereas 13C-4-glutamine was 5.68 +/- 1.84%. Steady-state modeling of the 13C label distribution in glutamate and glutamine suggests that, under these conditions, the consumption of the beta-hydroxybutyrate is predominantly neuronal, used at a rate of 0.032 +/- 0.009 mmol. kg-1. min-1, and accounts for 6.4 +/- 1.6% of total acetyl coenzyme A oxidation. These results are consistent with minimal accumulation of cerebral ketones with rapid utilization, implying blood-brain barrier control of ketone oxidation in the nonfasted adult human brain.

Effect of beta-hydroxybutyrate, a cerebral function improving agent, on cerebral hypoxia, anoxia and ischemia in mice and rats

Although improving energy metabolism in ischemic brain has been accepted for the treatment of cerebrovascular diseases, administration of glucose, as an energy substrate, would aggravate ischemic brain damage via activating anaerobic glycolysis, which leads to lactate accumulation. Beta-hydroxybutyrate (BHB) is one of the ketone bodies that can be utilized as an energy source during starvation. The purpose of our study was to define the protective effects of BHB on brain damage induced by hypoxia, anoxia and ischemia. The isotonic solution of BHB administered 30 min before the induction of ischemia at doses over 50 mg x kg(-1) x h(-1) showed remarkable protective effects against hypoxia and anoxia. BHB administered immediately after a bilateral carotid artery ligation at a dose of 30 mg x kg(-1) x h(-1) significantly suppressed the elevation of cerebral water and sodium contents as well as maintaining high ATP and low lactate levels. In contrast, glycerin, a hypertonic agent, substantially reduced the water content but did not show any significant effect on other parameters. We demonstrated that BHB, unlike glycerin, when used as an energy substrate in ischemic brain, has protective effects on cerebral hypoxia, anoxia and ischemia-induced metabolic change.

Suppression of feed intake after parenteral administration of D-beta-hydroxybutyrate in pygmy goats

The effect of intraperitoneal injection of D,L- or D-beta-hydroxybutyrate on feed intake and plasma metabolites was investigated in pygmy goats. The combined intraperitoneal injection of D,L-beta-hydroxybutyrate or D-beta-hydroxybutyrate (15 mmol/kg0.75) and 1,3-butanediol (6.6 mmol/kg0.75), a ketogenic substrate, decreased cumulative food intake while the same dose of 1,3-butanediol or DL-beta-hydroxybutyrate alone had no effect. The decrease in food intake after combined injection of D-beta-hydroxybutyrate and 1,3-butanediol was characterized by a significant decrease in meal frequency and a prolongation of the latency to eat. The hypophagic effect of the combined injection of D-beta-hydroxybutyrate and 1,3-butanediol was significant for 8 h, while the hypophagia after D,L-beta-hydroxybutyrate and 1,3-butanediol was significant for only 2 h after injection. Injection of D,L-beta-hydroxybutyrate increased plasma D-beta-hydroxybutyrate levels to 0.55 mmol/l and decreased plasma free fatty acids. Addition of 1,3-butanediol (6.6 mmol/kg0.75) to the injection increased plasma D-beta-hydroxybutyrate level up to 0.75 mmol/l. The results show that parenteral administration of D-hydroxybutyrate reduces feed intake in pygmy goats and that the hypophagia appears to be related to the amount of D-beta-hydroxybutyrate injected. The hypophagia seems to be related to elevated plasma D-beta-hydroxybutyrate concentration, and the threshold concentration appeared to be about 0.7 mmol/l under the experimental conditions of this study.