Infusion Of Beta-hydroxybutyrate Research Articles

Adaptive Metabolic Responses Facilitate Blood-Brain Barrier Repair in Ischemic Stroke via BHB-Mediated Epigenetic Modification of ZO-1 Expression.

Adaptive metabolic responses and innate metabolites hold promising therapeutic potential for stroke, while targeted interventions require a thorough understanding of underlying mechanisms. Adiposity is a noted modifiable metabolic risk factor for stroke, and recent research suggests that it benefits neurological rehabilitation. During the early phase of experimental stroke, the lipidomic results showed that fat depots underwent pronounced lipolysis and released fatty acids (FAs) that feed into consequent hepatic FA oxidation and ketogenesis. Systemic supplementation with the predominant ketone beta-hydroxybutyrate (BHB) is found to exert discernible effects on preserving blood-brain barrier (BBB) integrity and facilitating neuroinflammation resolution. Meanwhile, blocking FAO-ketogenesis processes by administration of CPT1α antagonist or shRNA targeting HMGCS2 exacerbated endothelial damage and aggravated stroke severity, whereas BHB supplementation blunted these injuries. Mechanistically, it is unveiled that BHB infusion is taken up by monocarboxylic acid transporter 1 (MCT1) specifically expressed in cerebral endothelium and upregulated the expression of tight junction protein ZO-1 by enhancing local β-hydroxybutyrylation of H3K9 at the promoter of TJP1 gene. Conclusively, an adaptive metabolic mechanism is elucidated by which acute lipolysis stimulates FAO-ketogenesis processes to restore BBB integrity after stroke. Ketogenesis functions as an early metabolic responder to restrain stroke progression, providing novel prospectives for clinical translation.

Infusions of beta-hydroxybutyrate, an endogenous NLRP3 inflammasome inhibitor, produce antidepressant-like effects on learned helplessness rats through BDNF-TrkB signaling and AMPA receptor activation, and strengthen learning ability

Beta-hydroxybutyrate (BHB), an endogenous NLRP3 inflammasome inhibitor, has been shown to be associated with the pathophysiology of depression in rodents. However its active mechanism has not been revealed. Herein, we probed both the pathways and brain regions involved in BHB's antidepressant-like effects in a learned helplessness (LH) rat model of depression. A single bilateral infusion of BHB into the cerebral ventricles induced the antidepressant-like effects on the LH rats. The antidepressant-like effects of BHB were blocked by the TrkB inhibitor ANA-12 and the AMPA receptor antagonist NBQX, indicating that the antidepressant-like effects of BHB involve BDNF-TrkB signaling and AMPA receptor activation. Further, infusions of BHB into the prelimbic and infralimbic portions of medial prefrontal cortex, the dentate gyrus of hippocampus, and the basolateral region of amygdala produced the antidepressant-like effects on LH rats. However, infusions of BHB into the central region of amygdala, the CA3 region of hippocampus, and the shell and core regions of nucleus accumbens had no effect. Finally, a single bilateral infusion of BHB into the cerebral ventricles of naive rats strengthened learning ability on repeated active avoidance test where saline-infused animals failed to increase avoidance responses.

#1315139: Cardiometabolic Effects of Elevated Plasma Ketones in Patients with Heart Failure and T2DM

This research study aims to discern the mechanism(s) responsible for the cardiac benefits of sodium-glucose cotransporter-2 (SGLT2) inhibitors. SGLT2 inhibitors induce systemic ketosis, but whether this is a mechanism of benefit in relation to improved cardiac function is currently unclear. To further elucidate this relationship, the effect of increased ketone concentration (with infusion of beta-hydroxybutyrate [BOHB]) on left ventricular (LV) function and myocardial glucose uptake (MGU) was done.

175-OR: Effect of Hyperketonemia on Cardiac Efficiency in Patients with Heart Failure and Type 2 Diabetes

Mechanism (s) responsible for the cardiac benefits of SGLT2 inhibitors remain unknown. Aim: To examine the effect of increased ketone concentration (with infusion of beta-hydroxybutyrate [BOHB]) on left ventricular (LV) function and myocardial glucose uptake (MGU) Methods: Two groups (12 per group) of T2DM with HFrEF (<45%) were studied. Group I (Age=60; BMI=32 kg/m2; A1c = 7.7%) received randomly a 6-hr BOHB infusion (Prime =1.5 mg/kg.min, then 0.75 mg/kg.min) or 6-hr HCO3 infusion (control) . Group II (Age=57; BMI=32 kg/m2; A1c=7%) received a 3-hr BOHB infusion at a higher rate. A cardiac MRI was performed before and after each infusion. Additionally, Group I underwent a PET study with 18FDG Results: Groups I and II achieved plasma ketone levels of 1.2 and 2.6 mmol/L respectively. In both groups, the BOHB infusion significantly (P<0.05) increased CO, stroke volume (SV) , and ejection fraction (EF) ; the increase in EF was greater in Group II vs. Group I (<0.001) (Figure 1) . NaHCO3 infusion had no effect on CO, SV, or EF. Myocardial glucose uptake was not altered by BOHB Conclusion: In patients with T2DM and HFrEF, increased plasma ketones significantly increases LV function and may be dose-dependent. These findings support the hypothesis that plasma ketones can provide an additional fuel for the heart, without interfering myocardial glucose metabolism and may be used therapeutically to improve cardiac function in HFrEF. Disclosure C.Solis-herrera: Speaker's Bureau; Novo Nordisk. Y.Qin: None. H.Honka: None. A.Moody: None. G.D.Clarke: None. C.L.Triplitt: Consultant; Bayer AG, Speaker's Bureau; Eli Lilly and Company, Novo Nordisk. E.Cersosimo: Research Support; AstraZeneca. R.A.Defronzo: Advisory Panel; AstraZeneca, Boehringer Ingelheim International GmbH, Intarcia Therapeutics, Inc., Novo Nordisk, Research Support; AstraZeneca, Boehringer Ingelheim International GmbH, Merck & Co., Inc., Speaker's Bureau; AstraZeneca. Funding Merck and Co and The Max and Minnie Tomerlin Voelcker Foundation and

Effect of elevated plasma ketones on cardiac efficiency

BackgroundThe mechanism(s) responsible for the cardiac benefits of SGLT2 inhibitors remain unknown. Specific AimTo examine the effect of increased plasma ketone concentration (with infusion of beta-hydroxybutyrate [BOHB]) on LV function and myocardial glucose uptake. MethodsTwo groups (6 per group) of T2DM with HFrEF (<45%) were studied. Group I (Age=59; BMI=31 kg/m2; A1c = 7.2%; EF=41%) received in random order a 6-hour BOHB infusion (Prime =1.5 mg/kg.min, then 0.75 mg/kg.min) or 6-hour HCO3 infusion with matching volume (control). Group II (Age=56; BMI=34 kg/m2; A1c=7.2%; EF=38%) received a 3-hour BOHB infusion at a higher rate (Prime=4.0 mg/kg.min, then 2.0 mg/kg.min). A cardiac MRI was performed before and after each infusion. Additionally, Group I underwent a PET study with 18F-2-DOG and 15O. ResultsGroups I and II achieved plasma ketone levels of 1.4 and 2.5 mmol/L, respectively. In Group II, BOHB infusion significantly (P<0.01) increased CO and EF, whereas in Group I the increase in CO and EF tend toward significance (p=0.06), suggesting a dose-dependent response to the increase in plasma ketone concentration. NaHCO3 infusion had no effect on any cardiac indices (Fig.1). Myocardial blood flow increased significantly (P<0.01) in both Group I and II. Myocardial glucose uptake was not altered by BOHB infusion. ConclusionIn patients with T2DM and HFrEF, a physiologic increase in plasma ketone concentration significantly increased LV function and myocardial blood flow without affecting cardiac glucose metabolism. These results suggest that altered myocardial substrate metabolism can be employed therapeutically to improve cardiac function in HFrEF.

Hepatic mRNA abundance of genes related to nuclear erythroid 2-related factor 2 changes in response to 48 h manipulated plasma metabolites and insulin in dairy cows: Metabolites and insulin infusion effects in cows

The endocrine and metabolic changes in early lactating dairy cows can induce inflammation through reactive oxygen species (ROS) impairing liver function. Nuclear erythroid 2-related factor 2 (Nrf2) is a transcription factor which regulates the expression of genes encoding antioxidative proteins which diminish inflammatory damage, neutralize ROS and suppress pro-inflammatory signaling, thereby protecting the liver. The aim was to investigate hepatic mRNA abundance of genes regulated by Nrf2 in response to a long-term (48 h) insulin or beta-hydroxybutyrate (BHB) infusion in 24 mid-lactating dairy cows. Treatments included 1) hyperinsulinemic clamp infusion (HypoG, n = 5), 2) hyperinsulinemic euglycemic clamp (EuG, n = 6), 3) BHB infusion (HyperB, n = 5), and 4) NaCl infusion (Control, n = 6). Liver tissue was sampled one week before and 48 h after the start of the infusion. Changes of hepatic mRNA abundances of candidate genes assessed via qPCR were evaluated by analysis of variance (ANOVA). Hyperinsulinemia euglycemic clamp downregulated mRNA abundance of microsomal glutathione S-transferase 3 (MGST3), MT1E, MT2A, glutathione peroxidase 3 (GPX3), superoxide dismutase 1(SOD1), catalase (CAT), and NAD (P) H dehydrogenase quinone 1(NQO1) compared to pre-infusions. The mRNA abundance of metallothionein 1A (MT1A) showed a tendency to increase in HyperB in comparison to pre-infusion level. Lower mRNA abundances of MT1E, MGST3, and SOD1 were observed in EuG compared to Control. The mRNA abundance of NQO1 was lower in EuG in comparison to HyperB. Downregulation of candidate genes could be related to reduced hepatic gluconeogenesis, since both high plasma insulin and low glucagon secretion levels were observed in EuG. Downregulation of Nrf2’s antioxidant enzymes may result in reduced liver protection, thereby contributing to impaired hepatic metabolism.

Beta-hydroxybutyrate infusion identifies acutely differentially expressed genes related to metabolism and reproduction in the hypothalamus and pituitary of castrated male sheep.

To identify molecular pathways that couple metabolic imbalances and reproduction, we randomly assigned 10 castrated male sheep to be centrally injected into the lateral ventricle through intracerebroventricular cannulas with 1 ml of β-hydroxybutyric acid sodium salt solution (BHB; 12,800 µmol/l) or saline solution (CON; 0.9% NaCl). Approximately 2 h postinjection, sheep were humanely euthanized, and hypothalamus and pituitary tissues were harvested for transcriptome characterization by RNA sequencing. RNA was extracted from the hypothalamus and pituitary and sequenced at a high depth (hypothalamus: 468,912,732 reads; pituitary: 515,106,092 reads) with the Illumina Hi-Seq 2500 platform and aligned to Bos taurus and Ovis aries genomes. Of the total raw reads, 87% (hypothalamus) and 90.5% (pituitary) mapped to the reference O. aries genome. Within these read sets, ~56% in hypothalamus and 69% in pituitary mapped to either known or putative protein coding genes. Fragments per kilobase of transcripts per million normalized counts were averaged and ranked to identify the transcript expression level. Gene Ontology analysis (DAVID Bioinformatics Resources) was utilized to identify biological process functions related to genes shared between tissues, as well as functional categories with tissue-specific enrichment. Between CON- and BHB-treated sheep, 11 and 44 genes were differentially expressed (adj. P < 0.05) within the pituitary and hypothalamus, respectively. Functional enrichment analyses revealed BHB altered expression of genes in pathways related to stimulus perception, inflammation, and cell cycle control. The set of genes altered by BHB creates a foundation from which to identify the signaling pathways that impact reproduction during metabolic imbalances.

0865 Beta-hydroxybutyrate infusion affects glucose metabolism before and after parturition in dairy cows

0865 Beta-hydroxybutyrate infusion affects glucose metabolism before and after parturition in dairy cows

Is on-admission capillary blood beta-hydroxybutyrate concentration associated with the acute stroke severity and short-term functional outcome?

Objectives: In conditions with reduced glucose levels/inability of glucose utilization, ketone bodies, especially beta-hydroxybutyrate (BHB), become a major energy source in the brain. In animal models, BHB infusion shows acute beneficial effects on the hypoxic brain. The present prospective observational study is the first to assess the relationship between on-admission capillary blood BHB levels and acute stroke severity/short-term functional outcomes.Methods: A total of 51 consecutive first-ever stroke patients (46 ischemic stroke) admitted within 24 hours since the symptom onset and ≤44 hours since the last meal were evaluated for stroke severity (National institutes of health stroke scale, NIHSS) and for disability (modified Rankin scale, mRS) 3 months post-stroke.Results: On-admission BHB values ranged between 0 and 1·6 mmol/l, with 43 (84·3%) values ≤0·4 mmol/l (normal). Higher BHB values were independently associated with longer fasting and hyperglycemia, whereas lower values were associated with dyslipidemia and diabetes. No association between on-admission BHB levels and NIHSS scores at presentation or day 5 was observed. The BHB levels considered either as continuous or as binary (>0·4 vs ≤0·4 mmol/l) variables were independently (adjustment for age, NIHSS score at presentation, fasting period, stroke type, hyperglycemia, diabetes, and dyslipidemia) associated with lower odds of mRS 0–2 (non-to-mild disability) 3 months post-stroke: OR = 0·09 (95% CI 0·00–0·97, P = 0·047) and OR = 0·07 (95% CI 0·00–0·78, P = 0·028), respectively.Discussion: This preliminary study suggests that higher on-admission BHB values are associated with poorer stroke outcomes and emphasizes the need for further investigations.

Calorie sources and recovery from central nervous system ischemia

Glucose is the primary substrate for the energy requirements of the nervous system. Nevertheless, administration of glucose to critically ill patients with central nervous system trauma may have adverse effects on their neurologic recovery. The purpose of this study was to evaluate the effects of other sources of nonprotein calories on spinal cord lactate accumulation and on electrophysiologic recovery after a period of severe spinal cord ischemia. Two randomized, blinded studies were performed: one of glycolytic energy substrates (fructose, xylitol, sorbitol, glycerol) and one of ketogenic energy substrates (beta-hydroxybutyrate, acetate, butyrate). College teaching hospital laboratory. New Zealand albino rabbits (weight 3.5 to 4.5 kg). After infusion of the randomly assigned treatment, temporary ischemia was produced in the lumbosacral spinal cord by occluding the abdominal aorta with a balloon catheter. Blood concentrations of glucose, lactate, pyruvate, and ketone bodies and spinal cord dialysate concentration of lactate were measured before and after infusion of the assigned treatment, and during ischemia and during the first 2 hrs after reperfusion. Spinal somatosensory evoked potentials were recorded during ischemia to assure a similar severity of ischemia in all animals and during the first 2 hrs after reperfusion as a measure of electrophysiologic recovery. Infusion of the glycolytic nutrients xylitol and fructose increased blood glucose and lactate concentrations, and resulted in increased lactate accumulation in the spinal cord during ischemia and resulted in a significantly poorer recovery of the spinal somatosensory evoked potential than infusion of saline. Infusion of sorbitol and glycerol did not have these adverse effects in the doses administered. None of the ketogenic nutrients increased blood glucose concentration or increased lactate accumulation in the spinal cord during ischemia when compared with infusion of saline. Infusion of butyrate and acetate caused arterial hypotension and resulted in a poorer recovery of the spinal somatosensory evoked potential than saline. Infusion of beta-hydroxybutyrate did not have an adverse effect on blood pressure or on evoked potential recovery. Glycerol, sorbitol, and beta-hydroxybutyrate deserve further evaluation as potential nonprotein calorie sources in patients with neurologic injury. Xylitol and fructose are not suitable since these substrates resulted in hyperglycemia and increased lactate accumulation in the central nervous system, and had detrimental effects on electrophysiologic recovery after ischemia. The short-chain fatty acids (acetate and butyrate) also had adverse effects on electrophysiologic recovery after ischemia, probably because of their hypotensive effects when given intravenously, rather than from the effects of their metabolism.

Effect of beta-hydroxybutyrate on whole-body leucine kinetics and fractional mixed skeletal muscle protein synthesis in humans.

Because intravenous infusion of beta-hydroxybutyrate (beta-OHB) has been reported to decrease urinary nitrogen excretion, we investigated in vivo metabolism of leucine, an essential amino acid, using L-[1-13C]leucine as a tracer during beta-OHB infusion. Leucine flux during beta-OHB infusion did not differ from leucine flux during normal saline infusion in nine normal subjects, whereas leucine oxidation decreased 18-41% (mean = 30%) from 18.1 +/- 1.1 mumol.kg-1.h-1 (P less than 0.01), and incorporation of leucine into skeletal muscle protein increased 5-17% (mean = 10%) from 0.048 + 0.003%/h (P less than 0.02). Since blood pH during beta-OHB infusion was higher than the pH during saline infusion, we performed separate experiments to study the effect of increased blood pH on leucine kinetics by infusing sodium bicarbonate intravenously. Blood pH during sodium bicarbonate infusion was similar to that observed during the beta-OHB infusion, but bicarbonate infusion had no effect on leucine flux or leucine oxidation. We conclude that beta-OHB decreases leucine oxidation and promotes protein synthesis in human beings.

The effect of ketone bodies on leucine and alanine metabolism in dogs

1. The effect of an infusion of sodium beta-hydroxybutyrate on leucine and alanine metabolism was investigated in dogs starved for 12 h. To determine whether the metabolic changes produced by this infusion were due to the resultant alkalaemia the effect of an equimolar infusion of sodium bicarbonate was also studied. 2. The sodium beta-hydroxybutyrate infusion reduced alanine concentration as a result of a decrease in alanine production rate and an increase in alanine metabolic clearance rate. The sodium bicarbonate infusion induced a small decrease in alanine concentration which was due to an increased metabolic clearance rate. Alanine production rate showed no change. This demonstrates that the fall in alanine concentration after a sodium beta-hydroxybutyrate infusion is due both to a ketone-specific inhibitory effect on alanine production rate and an increased metabolic clearance rate caused by the alkalaemia. 3. Leucine concentration was increased after the ketone infusion due to a small increase in production rate and there was a small increase in the rate of leucine incorporation into protein. Alkalaemia had no effect on leucine concentration or metabolism.

Effect of hyperketonemia on renal ammonia excretion in man

The effect of dl-sodium beta-hydroxybutyrate (Na BOHB) on urinary ammonia excretion was studied in seven chronically acidemic human subjects. Metabolic acidosis was induced by the ingestion of 0.1 g/kg body weight of ammonium chloride for three days. On the morning of day 4, baseline blood and urine samples were collected during three 30-minute periods. Na BOHB (1 mmol/kg, pH = 7.4) was then infused over 20 minutes, and this was followed by a continuous infusion at the rate of 10 μmol/kg min for 160 minutes. Urinary ammonia excretion decreased by 35% ( P < 0.001) while urine pH rose slightly from 5.49 to 5.82 ( P < 0.002). Venous pH increased from 7.31 to 7.38 ( P < 0.005) and bicarbonate concentration from 19 to 25 mEq/L ( P < 0.002). Four subjects were restudied with an infusion of Na β-OHB (pH adjusted to 4.4 with the addition of HCl). Venous pH and bicarbonate concentration did not change significantly while urine pH decreased from 5.25 to 4.90 ( P < 0.001). Urinary ammonia excretion fell by 34% ( P < 0.01) despite the decline in urine pH and the absence of change in blood pH and bicarbonate concentration. Three subjects were restudied with sodium bicarbonate (0.52 to 0.85 mEq/min) infusion. Despite similar increases in blood pH and plasma bicarbonate concentration as observed with Na β-OHB at pH = 7.4, urinary ammonia excretion did not fall significantly. In an attempt to simulate the change in redox potential and NAD + to NADH ratio that occurred during the metabolism of beta-hydroxybutyrate to acetoacetate, sodium lactate was given to four subjects. Urine pH, blood pH, and plasma bicarbonate concentration rose similarly to that observed with Na β-OHB infusion (pH = 7.4). Ammonia excretion declined by 35% ( P < 0.01). We conclude that the acute infusion of beta-hydroxybutyrate in acidemic man inhibits the urinary excretion of ammonia. These results can not be explained by changes in acid-base status, urine pH, renal plasma flow, or glomerular filtration rate. A change in intracellular redox potential may, in part, account for the decline in renal ammonia excretion.

A dual-isotope technique for determination of in vivo ketone body kinetics.

"Total ketone body specific activity" has been widely used in studies of ketone body metabolism to circumvent so-called "isotope disequilibrium" between the two major ketone body pools, acetoacetate and beta-hydroxybutyrate. Recently, this approach has been criticized on theoretical grounds. In the present studies, [13C]acetoacetate and beta-[14C]hydroxybutyrate were simultaneously infused in nine mongrel dogs before and during an infusion of either unlabeled sodium acetoacetate or unlabeled sodium beta-hydroxybutyrate. Ketone body turnover was determined using total ketone body specific activity, total ketone body moles % enrichment, and an open two-pool model, both before and during the exogenous infusion of unlabeled ketone bodies. Basal ketone body turnover rates were significantly higher using [13C]acetoacetate than with either beta-[14C]hydroxybutyrate alone or the dual-isotope model (3.6 +/- 0.5 vs. 2.2 +/- 0.2 and 2.7 +/- 0.2 mumol X kg-1 X min-1, respectively, P less than 0.05). During exogenous infusion of unlabeled sodium acetoacetate, the dual-isotope model provided the best estimate of ketone body inflow, whereas 14C specific activity underestimated the known rate of acetoacetate infusion by 55% (P less than 0.02). During sodium beta-hydroxybutyrate infusion, [13C]-acetoacetate overestimated ketone body inflow by 55% (P = NS), while better results were obtained with 14C beta-hydroxybutyrate alone and the two-pool model. Ketone body interconversion as estimated by the dual-isotope technique increased markedly during exogenous ketone body infusion. In conclusion, significant errors in estimation of ketone body inflow were made using single-isotope techniques, whereas a dual-isotope model provided reasonably accurate estimates of ketone body inflow during infusion of exogenous acetoacetate and beta-hydroxybutyrate.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of muscular triglyceride lipolysis by ketone bodies: a mechanism for energy-preservation in starvation.

Using the forearm technique, muscle substrate balances were measured in healthy volunteers under the influence of a low dose intraarterial infusion of beta-hydroxybutyrate. The ketone body led to a prompt cessation of muscular release of glycerol and free fatty acids, indicating inhibited muscular triglyceride lipolysis. This finding confirms the concept of substrate regulation of muscle triglyceride lipolysis in vivo.

Regulation of the glycine cleavage system in the isolated perfused rat liver.

The catabolism of glycine in the isolated perfused rat liver was investigated by measuring the production of 14CO2 from [1-14C]- and [2-14C]glycine. Production of 14CO2 from [1-14C]glycine was maximal as the perfusate glycine concentration approached 10 mM and exhibited a maximal activity of 125 nmol of 14CO2 X g-1 X min-1 and an apparent Km of approximately 2 mM. Production of 14CO2 from [2-14C]glycine was much lower, approaching a maximal activity of approximately 40 nmol of 14CO2 X g-1 X min-1 at a perfusate glycine concentration of 10 mM, with an apparent Km of approximately 2.5 mM. Washout kinetic experiments with [1-14C]glycine exhibited a single half-time of 14CO2 disappearance, indicating one metabolic pool from which the observed 14CO2 production is derived. These results indicate that the glycine cleavage system is the predominant catabolic fate of glycine in the perfused rat liver and that production of 14CO2 from [1-14C]glycine is an effective monitor of metabolic flux through this system. Metabolic flux through the glycine cleavage system in the perfused rat liver was inhibited by processes which lead to reduction of the mitochondrial NAD(H) redox couple. Infusion of beta-hydroxybutyrate or octanoate inhibited 14CO2 production from [1-14C]glycine by 33 and 50%, respectively. Alternatively, infusion of acetoacetate stimulated glycine decarboxylation slightly and completely reversed the inhibition of 14CO2 production by octanoate. Metabolic conditions which are known to cause a large consumption of mitochondrial NADPH (e.g. ureogenesis from ammonia) stimulated glycine decarboxylation by the perfused rat liver. Infusion of pyruvate and ammonium chloride stimulated production of 14CO2 from [1-14C]glycine more than 2-fold. Lactate plus ammonium chloride was equally as effective in stimulating glycine decarboxylation by the perfused rat liver, while alanine plus ammonium chloride was ineffective in stimulating 14CO2 production.

Cardiovascular and biochemical effects of infusion of beta hydroxybutyrate into the fetal lamb

Previous studies from our laboratory have shown that beta hydroxybutyrate crosses the ovine placenta in small amounts during maternal hyperketonemia and produces significant reductions in fetal PaO2 and increased fetal lactate levels. The present study evaluates the effects of fetal hyperketonemia on fetal and maternal cardiovascular and biochemical parameters. Pregnant ewes (110 to 120 days' gestation) were instrumented with catheters in the femoral artery, femoral vein, and uterine veins, and electromagnetic flow probes were placed on the middle uterine arteries. The fetal carotid artery and jugular vein were catheterized, and a catheter and balloon were placed in the amniotic fluid. Beta hydroxybutyrate (0.44 mmole/min) and antipyrine (0.03 mmole/min) were simultaneously infused directly into the fetal jugular vein for 90 minutes. The fetal beta hydroxybutyrate level increased from a baseline of 0.12 ± 0.08 to 6.80 ± 0.46 mmoles/L and was associated with a significant decrease in fetal PaO2 (23.7 ± 2.4 to 16.0 ± 0.4 mm Hg) and a large increase in the fetal lactate level (1.85 ± 0.27 to 5.43 ± 0.92 mmoles/L) at 90 minutes. The present results suggest that during fetal hyperketonemia fetal oxygenation is significantly reduced and may contribute to the increased perinatal mortality in the pregnant diabetic patient.

Hepatic versus cerebral origin of stimulus for feeding induced by 2-deoxy-d-glucose in rats.

Intravenous administration of 2-deoxy-D-glucose (2-DG), a competitive inhibitor of glucose utilization, increased the food intake of rats. Infusions of glucose or mannose abolished this effect, whereas equimolar fructose solutions did not affect 2-DG-induced feeding. Similar results were obtained when 2-DG and the hexoses were administered into the hepatic portal vein. These findings suggest that 2-DG elicits feeding due to glucoprivation at a site that is inaccessible to fructose. This site is likely to be in the brain, not the liver, because all three sugars can nourish peripheral tissue but only fructose cannot penetrate the blood-brain barrier. Moreover, 2-DG-induced feeding was abolished by intravenous infusion of beta-hydroxybutyrate, a substrate that can be oxidized by brain and other tissues but not by the liver.

The effect of ketone bodies on renal ammoniogenesis.

Infusion of ketone bodies to ammonium chloride-loaded acidotic dogs was found to induce significant reduction in urinary excretion of ammonia. This effect could not be attributed to urinary pH variations. Total ammonia production by the left kidney was measured in 25 animals infused during 90 min with the sodium salt of D,L-beta-hydroxybutyric acid adjusted to pH 6.0 or 4.2. Ketonemia averaged 4.5 mM/liter. In all experiments the ammonia content of both urine and renal venous blood fell markedly so that ammoniogenesis was depressed by 60% or more within 60 min after the onset of infusion. Administration of equimolar quantities of sodium acetoacetate adjusted to pH 6.0 resulted in a 50% decrease in renal ammonia production. Infusion of ketone bodies adjusted to pH 6.0 is usually accompanied by a small increase in extracellular bicarbonate (3.7 mM/liter). However infusion of D,L-sodium lactate or sodium bicarbonate in amounts sufficient to induce a similar rise in plasma bicarbonate resulted in only a slight decrement in ammonia production (15%). The continuous infusion of 5% mannitol alone during 90-150 min failed to influence renal ammoniogenesis. Infusion of pure sodium-free beta-hydroxybutyric acid prepared by ion exchange (pH 2.2) resulted in a 50% decrease in renal ammoniogenesis in spite of the fact that both urinary pH and plasma bicarbonate fell significantly. During all experiments where ketones were infused, the renal extraction of glutamine became negligible as the renal glutamine arteriovenous difference was abolished. Renal hemodynamics did not vary significantly. Infusion of beta-hydroxybutyrate into the left renal artery resulted in a rapid decrease in ammoniogenesis by the perfused kidney. The present study indicates that ketone bodies exert their inhibitory influence within the renal tubular cell. Since their effect is independent of urinary or systemic acid-base changes, it is suggested that they depress renal ammoniogenesis by preventing the transformation of glutamine and glutamate into alpha-ketoglutarate in the mitochondria of the renal tubular cell.

Uric acid excretion in diabetic ketoacidosis.

Renal clearance studies in five patients during and after an episode of diabetic ketosis showed that there was decreased uric acid excretion and consequent elevation of the serum level. This was due to altered tubular handling of urate. Similar renal changes were produced by the infusion of beta-hydroxybutyrate in three normal subjects.