Differential effects of sodium acetoacetate and acetoacetic acid infusions on alanine and glutamine metabolism in man

Effects of ketone bodies on energy expenditure, substrate utilization, and energy intake in humans

The potential of ketogenic approaches to regulate energy balance has recently gained attention since ketones may influence both energy expenditure and energy intake. In this narrative review, we summarized the most relevant evidence about the role of ketosis on energy expenditure, substrate utilization, and energy intake in humans. We considered different strategies to induce ketosis, such as fasting, dietary manipulation, and exogenous ketone sources. In general, ketosis does not have a major influence on energy expenditure but promotes a shift in substrate utilization towards ketone body oxidation. The strategies to induce ketosis by reduction of dietary carbohydrate availability (e.g., ketogenic diets) do not independently influence energy intake, being thus equally effective for weight loss as diets with higher carbohydrate content. In contrast, the intake of medium-chain triglycerides and ketone esters induces ketosis and appears to increase energy expenditure and reduce energy intake in the context of high carbohydrate availability. These latter strategies lead to slightly enhanced weight loss. Unfortunately, distinguishing the effects of the various ketogenic strategies per se from the effects of other physiological responses is not possible with the available human data. Highly controlled, inpatient studies using targeted strategies to isolate the independent effects of ketones are required to adequately address this knowledge gap.

Starvation Ketosis and the Kidney

BACKGROUND

The remarkable ability of the body to adapt to long-term starvation has been critical for survival of primitive man. An appreciation of these processes can provide the clinician better insight into many clinical conditions characterized by ketoacidosis.

SUMMARY

The body adapts to long-term fasting by conserving nitrogen, as the brain increasingly utilizes keto acids, sparing the need for glucose. This shift in fuel utilization decreases the need for mobilization of amino acids from the muscle for purposes of gluconeogenesis. Loss of urinary nitrogen is initially in the form of urea when hepatic gluconeogenesis is dominant and later as ammonia reflecting increased glutamine uptake by the kidney. The carbon skeleton of glutamine is utilized for glucose production and regeneration of consumed HCO3-. The replacement of urea with NH4+ provides the osmoles needed for urine flow and waste product excretion. Over time, the urinary loss of nitrogen is minimized as kidney uptake of filtered ketone bodies becomes more complete. Adjustments in urine Na+ serve to minimize kidney K+ wasting and, along with changes in urine pH, minimize the likelihood of uric acid precipitation. There is a sexual dimorphism in response to starvation. Key Message: Ketoacidosis is a major feature of common clinical conditions to include diabetic ketoacidosis, alcoholic ketoacidosis, salicylate intoxication, SGLT2 inhibitor therapy, and calorie sufficient but carbohydrate-restricted diets. Familiarity with the pathophysiology and metabolic consequences of ketogenesis is critical, given the potential for the clinician to encounter one of these conditions.

Can ketone bodies inactivate coronavirus spike protein? The potential of biocidal agents against SARS-CoV-2

Biocidal agents such as formaldehyde and glutaraldehyde are able to inactivate several coronaviruses including SARS-CoV-2. In this article, an insight into one mechanism for the inactivation of these viruses by those two agents is presented, based on analysis of previous observations during electron microscopic examination of several members of the orthocoronavirinae subfamily, including the new virus SARS-CoV-2. This inactivation is proposed to occur through Schiff base reaction-induced conformational changes in the spike glycoprotein leading to its disruption or breakage, which can prevent binding of the virus to cellular receptors. Also, a new prophylactic and therapeutic measure against SARS-CoV-2 using acetoacetate is proposed, suggesting that it could similarly break the viral spike through Schiff base reaction with lysines of the spike protein. This measure needs to be confirmed experimentally before consideration. In addition, a new line of research is proposed to help find a broad-spectrum antivirus against several members of this subfamily.

Protein sparing during treatment of obesity: ketogenic versus nonketogenic very low calorie diet

Although it is generally agreed that both ketogenic and nonketogenic very low calorie diets promote weight reduction, there is no consensus on a preference of one diet over the other in regard to protein sparing. In the present study, we compared the effects of isocaloric (600 kcal/d) and isonitrogenous (8 g nitrogen/d) ketogenic (low carbohydrate) and nonketogenic diets on parameters of protein and amino acid metabolism, in 16 morbidly obese women maintained on these diets for 4 weeks while confined to a metabolic ward. Cumulative urinary nitrogen excretion (g/4 wk) was significantly (P less than .01) greater (248 +/- 6 v 207 +/- 12, mean +/- SEM, n = 8), and cumulative nitrogen balance significantly (P less than .02) more negative (-50.4 +/- 4.4 v -18.8 +/- 5.7), during treatment with the ketogenic than with the nonketogenic diet. Plasma leucine concentration (mumol/L) was significantly higher (P less than .05) during treatment with the ketogenic than with the nonketogenic diet at day 14 (210 +/- 17 v 150 +/- 8), but not at day 28 (174 +/- 9 v 148 +/- 8). Whole-body rates of leucine oxidation (mmol/h) were significantly higher (P less than .05) during treatment with the ketogenic than with the nonketogenic diet at day 14 (1.29 +/- 0.20 v 0.92 +/- 0.10) and at day 28 (1.00 +/- 0.16 v 0.75 +/- 0.10). Conversely, proteolysis, as measured by leucine turnover rate and urinary excretion of 3-methylhistidine, was not significantly different between the diets.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of ketone bodies on nitrogen metabolism in skeletal muscle

1. The ketone bodies, D-beta-hydroxybutyrate and acetoacetate, inhibit glycolysis thereby reducing pyruvate availability which leads to a marked inhibition of branched-chain amino acid metabolism and alanine synthesis in skeletal muscles from fasted mammalian and avian species. 2. The rate of glutamine release from skeletal muscles from fasted birds is increased at the expense of alanine in the presence of elevated concentrations of ketone bodies because of an increase in the availability of glutamate for glutamine synthesis. 3. Ketone bodies inhibit both protein synthesis and protein degradation in skeletal muscles from fasted mammalian and avian species in vitro. The mechanisms involved remain unknown. 4. Inhibition of amino acid metabolism and protein turnover in skeletal muscle by ketone bodies may be an important survival mechanism during adaptation to catabolic states such as prolonged fasting.

Substrate metabolism during modest hyperinsulinemia in response to isolated hyperketonemia in insulin-dependent diabetic subjects

To assess the metabolic effects of moderate hyperketonemia, six young male type 1 diabetic patients received a 200-minute intravenous (IV) infusion of (1) 0.9 mmol 3-hydroxybutyrate (3-OHB)/kg/h, and (2) saline. To ensure comparable metabolic conditions, a low-dose hyperinsulinemic euglycemic glucose clamp was performed from 5 hours before and throughout 3-OHB/saline infusions. The forearm technique was employed to estimate substrate fluxes in muscle. Infusion of 3-OHB caused: (1) increases (P less than .05) in circulating levels of 3-OHB (from 112 +/- 73 mumol/L to 825 +/- 111 mumol/L) and forearm arteriovenous differences of 3-OHB (from 19 +/- 10 mumol/L to 145 +/- 46 mumol/L), as well as an eightfold increase of plasma acetoacetate. (2) Decreased (P less than .05) levels of nonesterified fatty acids (NEFA; from 466 +/- 85 mumol/L to 201 +/- 14 mumol/L) and glycerol (from 39 +/- 7 mumol/L to 11 +/- 4 mumol/L) and decreased (P less than .05) arteriovenous differences of glycerol (from -16 +/- 8 mumol/L to -3 +/- 2 mumol/L). (3) Increased (P less than .05) levels of serum growth hormone (GH; from 4.1 +/- 1.5 micrograms/L to 15.9 +/- 8.0 micrograms/L). No change was recorded in circulating concentrations of free insulin, glucagon, glucose, lactate, or alanine. Nor were arteriovenous balances of these intermediary metabolites, isotopically determined glucose turnover or amounts of exogenously administered glucose affected. In conclusion, in type 1 diabetic man, the main regulatory effect of isolated hyperketonemia appears to be a direct negative feedback inhibition of lipolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Ketone bodies and islet function: 86Rb handling and metabolic data

The metabolism of ketone bodies was investigated in rat pancreatic islets incubated in the absence or presence of D-glucose. The generation of 14CO2 from 3-14C-labeled ketone bodies, the interconversion of D-(-)-beta-hydroxybutyrate and acetoacetate (AcAc), the reciprocal effects of ketone bodies and D-glucose on their respective catabolism, and the influence of these exogenous nutrients on the output of 14CO2 from islets preincubated with either L-[U-14C]glutamine or [U-14C]palmitate provided an estimation of the nutrient-induced changes in O2 uptake that was in fair agreement with the observed modifications of islet respiration. There was a close correlation between such changes and the corresponding values for insulin output. Because the stimulation of insulin release by ketone bodies also coincided with a decrease in 86Rb outflow from prelabeled islets, these findings suggest that the insulinotropic action of ketone bodies is causally linked to their catabolism through an increase in ATP generation rate and a subsequent decrease in K+ conductance. A complementary participation of changes in mitochondrial redox state to stimulus-secretion coupling is considered, however, in the light of comparisons between the effects of D-(-)-beta-hydroxybutyrate and AcAc, respectively, on mitochondrial NADH generation, 45Ca net uptake, and D-[6-14C]glucose oxidation.

Ketone body production and disposal: effects of fasting, diabetes, and exercise

Turnover studies performed during progressive fasting in normal subjects indicate that the production rate and the concentration of KB rise markedly during the early phase of fasting and start reaching a plateau after about 5 days. In addition to increased production, a reduction in the metabolic clearance rate of KB contributes to the hyperketonemia. This reduced metabolic clearance rate reflects essentially the progressive saturation of muscular ketone uptake that occurs with increasing ketonemia. The hormonal and metabolic environment of fasting plays only a minor role in this process, since a fall in KB metabolic clearance similar to that observed during fasting is observed if hyperketonemia is artificially induced in the postabsorptive state by the infusion of exogenous ketones. As extraction of KB by muscle becomes limited during ongoing fasting, KB are preferentially taken up by the brain to serve as a substrate replacing glucose. The remarkable stability of ketonemia during prolonged fasting is maintained through the operation of a negative feedback mechanism whereby KB tend to restrain their own production rate. The antilipolytic and insulinotropic effects of KB are instrumental in this process. This homeostatic mechanism maintains ketogenesis only slightly above the maximal metabolic disposal rate, the difference corresponding to urinary excretion, which is always below 10% of total turnover under physiologic conditions. When type I insulin-deprived diabetic patients are compared at the same KB concentration with control subjects with fasting ketosis, the characteristics of KB kinetics are comparable in the two groups. The maximal KB removal capacity is identical in the two situations, and it is not possible to identify a ketone removal defect specific to diabetes. Thus, these data favor the concept that excessive production of KB represent the main factor leading to uncontrolled hyperketonemia. It should be realized that a production exceeding only slightly that prevailing during prolonged fasting is sufficient to cause a progressive build-up in concentration, leading to uncontrolled diabetic ketosis. In the overnight-fasted state, a prolonged exercise (2 h) performed at moderate intensity (50% VO2 max) stimulates the capacity of muscle to extract ketones from blood as evidenced by a stimulation of the metabolic clearance rate.(ABSTRACT TRUNCATED AT 400 WORDS)

Plasma amino acids in relation to metabolic control in insulin-dependent diabetic children

The influence of metabolic control (estimated by blood glucose, 3-hydroxybutyrate and glycosylated hemoglobin levels) on plasma amino acids was determined in a group of 56 insulin-dependent diabetic children. A multiple correlation analysis revealed significant positive partial correlations between most amino acids and blood glucose. Alanine, methionine, tyrosine, phenylalanine and arginine showed negative partial correlations to the 3-hydroxybutyrate level. The results are consistent with the postulate that ketone body inhibition of muscle proteolysis is one of the factors regulating substrate flows during insulin deficiency.

The effect of glucose and insulin infusion on the fall of ketone bodies during treatment of diabetic ketoacidosis

During the treatment of diabetic ketoacidosis intravenous glucose is infused when blood glucose has fallen to around 14 mmol l-1. The use of hypertonic (10%) glucose has been recommended in order to hasten the clearance of blood ketone bodies. In a randomized controlled study 17 patients presenting with severe diabetic ketoacidosis were allocated to one of two regimens of intravenous glucose and insulin when blood glucose had fallen to less than 14 mmol l-1. Nine patients were given 5% glucose containing 10 U l-1 insulin and 8 patients received 10% glucose with 40 U l-1 insulin. Fluid was infused at a rate of 250 ml h-1 for 6 h. At the start of the infusions blood glucose had fallen from levels at presentation to 12.8 +/- 1.1 mmol l-1 (mean +/- SE) in the group which subsequently received the low infusion rate and to 13.7 +/- 0.9 mmol l-1 in the subsequent high infusion rate group. With glucose/insulin infusion blood glucose after 6 h was 11.5 +/- 0.9 mmol l-1 (low infusion rate group) and 15.7 +/- 1.3 mmol l-1 (high infusion rate group). This difference between groups at 6 h was significant (p less than 0.05). Over the 6 h of infusion the fall in blood total ketone bodies was significantly greater in the group receiving the higher rate of glucose/insulin infusion (7.34 +/- 0.57 vs 5.18 +/- 0.57 mmol l-1; p less than 0.05). Despite the greater fall in total ketone bodies in this group there was no difference in the improvement in capillary blood pH or bicarbonate.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Impact of methionine on net ketoacid production in humans

An exogenous acid load (NH4Cl) inhibits net ketoacid production in the first week of starvation and the fourth to eighth weeks of ketogenic dieting. To determine whether an acid load produced by amino acid metabolism can similarly modify ketosis, five overweight volunteers ingested methionine (H2SO4), NH4Cl, and NaCl (control), in varying order, each day for seven days during weeks 5 to 8 of hypocaloric ketogenic dieting. During days 5 to 7 of each phase, blood pH, bicarbonate, and pCO2 were stable but lower in the NH4Cl phase (7.32 +/- 0.02, 18.1 +/- 1.2 mmol/L, 35.8 +/- 1.4 mmHg) and the methionine phase (7.33 +/- 0.01, 17.1 +/- 0.9 mmol/L, 34.0 +/- 2.0 mmHg) than in the NaCl phase (7.38 +/- 0.01, 22.3 +/- 0.2 mmol/L, 37.6 +/- 1.6 mmHg), P less than .05. Over this period, blood acetoacetate concentration was lower during the methionine and NH4Cl phases than during NaCl, P less than .05. In addition blood beta-hydroxybutyrate and total ketone-body concentrations were lower in the methionine than NaCl phases, P less than .05. Urinary acetoacetate and beta-hydroxybutyrate excretion fell with both acid loads, P less than .05. Compared with control values, urinary total ketone excretion was suppressed by 67 +/- 10% in the NH4Cl and 89 +/- 3% in the methionine periods. When NaCl was ingested after either of the acid loads, urinary ketone excretion increased by 300% to 700%. Thus, methionine ingestion, which results in an acid challenge equivalent to that of a large protein load, has an impact on net ketoacid production similar to that of NH4Cl.(ABSTRACT TRUNCATED AT 250 WORDS)

Following weight loss in massively obese patients correction of the insulin resistance of fat metabolism is delayed relative to the improvement in carbohydrate metabolism

Intermediary metabolite and serum insulin concentrations have been measured during incremental intravenous low-dose insulin infusion in massively obese patients before, and 3 months and 12 months after gastroplasty. Fasting blood glucose was similar on the three occasions, but fasting serum insulin was significantly higher preoperatively and showed a progressive fall with weight loss. Significant negative linear correlations were found between serum insulin and blood glucose, plasma nonesterified fatty acids, blood glycerol and blood total ketone bodies concentrations. The insulin-glucose dose-response curve showed a significant left shift at 3 months with a further significant improvement at 12 months. No significant change in the responses for nonesterified fatty acids, glycerol, and ketone bodies was observed at 3 months, but all three showed a significant left shift at 12 months. Massively obese patients are resistant to the action of insulin on carbohydrate and fat metabolism. Weight loss following gastroplasty results in an improvement in sensitivity to insulin, which is evident earlier in carbohydrate metabolism than in fat metabolism.

Glucose-alanine relationship in normal human pregnancy

In order to quantify the glucose-alanine relationship in normal human pregnancy, the turnover rates of alanine and the incorporation of alanine carbon into glucose were quantified in 15 pregnant women during the last 4 weeks of gestation following a ten-hour fast. Eight nonpregnant women of similar age group were studied as controls. L-[2,3-13C2]Alanine and D[6,6-2H2]glucose were infused as tracers. The 13C enrichment of alanine, lactate, and glucose and the deuterium enrichment of glucose were measured by gas chromatography-mass spectrometry. In five pregnant and five nonpregnant women, the contribution of alanine carbon to expired CO2 directly and via glucose was estimated by combining indirect respiratory calorimetry with the tracer infusions. The alanine turnover rates in the pregnant and nonpregnant women were similar (pregnant, 4.43 +/- 0.82 mumol/kg x min; nonpregnant, 4.11 +/- 1.08 mumol/kg x min, mean +/- SD). However, the fraction of alanine incorporated into glucose was significantly lower during pregnancy (23.5 +/- 8.3% v 30.8 +/- 8.2%, P less than .04). In pregnant women, 20% of lactate pool was derived from alanine as compared with 28% in nonpregnant subjects (P less than .02). Twenty-four percent of alanine turnover was converted to CO2 in both pregnant and nonpregnant women. The plasma insulin concentration was increased significantly during pregnancy (P less than .05). These data suggest that gluconeogenesis from alanine is attenuated during pregnancy. This decrease in gluconeogenesis is not the result of decreased alanine flux, but due to intrinsic intrahepatic mechanism such as decreased deamination of alanine mediated by the predominant insulin effect or a decreased hepatic uptake of alanine.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic effects of combined oral contraceptive preparations

Fasting intermediary metabolite concentrations were measured in comparable groups of women either in the follicular or luteal phase of the menstrual cycle or taking low-dose estrogen combined oral contraceptive preparations. Blood total ketone bodies concentrations were significantly elevated in oral contraceptive users (p less than 0.05 v follicular and luteal groups) whilst blood alanine levels were lower (p less than 0.01 v follicular).

Inhibition of muscular amino acid release by lipid infusion in man

Amino acid balances of healthy postabsorptive volunteers were investigated with the forearm technique under the influence of an intravenous infusion of triglyceride emulsions (LCT; MCT/LCT) [corrected]. A decrease of the basal muscular release of most of the amino acids, respectively an increase of pre-existent uptake rates [corrected]. In parallel, arterial concentrations of these amino acids declined. With constant insulin levels and substantially unchanged blood glucose levels, this inhibition of muscular proteolysis and/or stimulation of proteosynthesis is most probably due to the increased level of free fatty acids.

Ketone bodies increase glomerular filtration rate in normal man and in patients with type 1 (insulin-dependent) diabetes mellitus

The purpose of this study was to investigate whether the administration of acetoacetic and hydrochloric acids in a group of control and Type 1 (insulin-dependent) diabetic patients influenced renal haemodynamics. Renal plasma flow increased from 657 +/- 88 to 762 +/- 81 ml X min-1. 1.73 m-2 in diabetic patients (p less than 0.01) and from 590 +/- 71 to 691 +/- 135 in control subjects (p less than 0.01). Glomerular filtration rate increased from 135 +/- 9 to 180 +/- 8 ml X min-1. 1.73 m-2 in diabetic patients (p less than 0.001) and from 117 +/- 8 to 145 +/- 7 in control subjects (p less than 0.01). Similar effects on renal haemodynamics, even if less pronounced, were observed with low dose acetoacetic but not with hydrochloric acid infusion. Total protein, beta 2-microglobulin but not albumin excretion rates were increased by acetoacetic acid. We conclude that an acute increase in blood concentration of ketone bodies within the range found in diabetic patients with poor metabolic control increases renal plasma flow and glomerular filtration rate both in control subjects and diabetic patients and causes a tubular proteinuria.

Role of acidosis in regulating hepatic nitrogen metabolism during fasting in conscious dog

This study was designed to investigate the role that acidosis plays in the metabolic responses to fasting. Eighteen conscious dogs with surgically implanted catheters in the femoral artery and in the hepatic, portal, and renal veins were studied. Six were fasted for 24 h and 12 were fasted for 4 days (96 h). On the day of the study, six 4-day fasted dogs were infused intravenously with NaHCO3 (10 mumol X kg-1 X min-1) for 3 h, while the rest received saline and acted as controls. Splanchnic balances of glutamine, alanine, blood urea nitrogen, ammonia, lactate, beta-hydroxybutyrate, and acetoacetate were estimated using the Fick principle. Blood flow to the splanchnic and renal beds were estimated using indocyanine green and p-aminohippurate extraction methods, respectively. The infusion of NaHCO3 nearly abolished the base deficit associated with fasting and normalized arterial bicarbonate levels but did not alter blood pH. It suppressed but did not abolish hepatic glutamine output by 60%. This was associated with a shift in cytoplasmic and mitochondrial redox potentials of the hepatocyte as evident by a decrease in hepatic production of beta-hydroxybutyrate and an increase in hepatic production of acetoacetate and a decrease in hepatic lactate utilization. Concomitantly, renal glutamine uptake decreased. Glutamine release of skeletal muscle was unchanged. The data suggest that hepatic glutamine synthesis and release seen with 4-day fasting has two components: a bicarbonate-dependent component that is influenced by the redox potential of the hepatocyte and a bicarbonate-independent component, the nature of which is not yet clear.(ABSTRACT TRUNCATED AT 250 WORDS)

Leucine metabolism in stable cirrhosis

Alterations in protein and amino acid metabolism have been postulated to explain the frequent observations of muscle wasting and decreased plasma branched-chain amino acid concentrations in cirrhosis. In order to investigate the changes in protein metabolism, we have measured the rates of leucine turnover and oxidation in six stable, biopsy-proven cirrhotics and six age and sex-matched healthy control subjects after an overnight fast, using [1-13C]leucine tracer. Following a primed constant-rate infusion of [1-13C]leucine, the 13C enrichments of plasma leucine and expired CO2 were used to estimate leucine turnover and oxidation, respectively. Fat-free body mass was estimated from the measurements of total body water as quantified by H2[18O] tracer dilution. The rates of CO2 production and oxygen consumption were measured hourly during the study period, using open-circuit respiratory calorimetry. Urinary urea, ammonia and total nitrogen excretion rates were quantified from timed urine samples. Even though the plasma leucine levels were lower in cirrhotics as compared with controls (100.5 +/- 17.1 vs. 138.3 +/- 20.4 mumoles per liter, mean +/- S.D., p less than 0.001), the rates of leucine turnover were not significantly different in the two groups (89.4 +/- 19.0 vs. 87.8 +/- 19.0 mumoles per kg X hr). In contrast, the rates of leucine oxidation were significantly reduced in cirrhosis (8.1 +/- 2.5 vs. 12.7 +/- 3.1 mumoles per kg X hr, p less than 0.01). When all subjects were considered, the leucine oxidation rate was correlated with plasma leucine concentration (r = 0.62, p less than 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous feeding--a review of aspects of current practice

This review summarises the present state of knowledge of energy and nitrogen requirements of hospital patients requiring intravenous feeding. It also addresses electrolyte, inorganic element and vitamin intakes, and examines possible differences in requirements in some special circumstances. It is concluded that most of the patients could be fed using one of a small number of standard regimens.

Metabolic effects of bicarbonate in the treatment of diabetic ketoacidosis

The effect of intravenous bicarbonate on the changes in intermediary metabolites during the initial treatment of diabetic ketoacidosis was examined in 16 patients. The results were compared with the changes seen in 16 patients receiving intravenous saline. Infusion of 150 mmol (mEq) bicarbonate significantly delayed the fall in blood lactate, lactate:pyruvate ratio, and total ketone bodies observed in the saline treated group. No difference in the rate of fall of blood glucose concentration was found. There is no metabolic indication for the use of intravenous bicarbonate in the treatment of diabetic ketoacidosis.

Effect of ketone bodies on glucose production and utilization in the miniature pig

The effect of ketone bodies on glucose production (Ra) and utilization (Rd) was investigated in the 24-h starved, conscious unrestrained miniature pig. Infusing Na-DL-beta-OH-butyrate (Na-DL-beta-OHB) and thus shifting the blood pH from 7.40 to 7.56 resulted in a decrease of Ra by 52% and of Rd by 45%, as determined by the isotope dilution technique. Simultaneously, the concentrations of arterial insulin and glucagon were slightly enhanced, whereas the plasma levels of glucose, lactate, pyruvate, alanine, alpha-amino-N, and free fatty acids (FFA) were all reduced. Infusion of Na-bicarbonate, which yielded a similar shift in blood pH, did not mimick these effects. Infusion of equimolar amounts of the ketoacid, yielding a blood pH of 7.35, induced similar metabolic alterations with respect to plasma glucose, Ra, Rd, and insulin; however, plasma alanine and alpha-amino-N increased. Infusing different amounts of Na-DL-beta-OHB resulting in plasma steady state levels of ketones from 0.25 to 1.5 mM had similar effects on arterial insulin and glucose kinetics. No dose dependency was observed. Prevention of the Na-DL-beta-OHB-induced hypoalaninemia by simultaneous infusion of alanine (1 mumol/kg X min) did not prevent hypoglycemia. Infusion of Na-DL-beta-OHB plus insulin (0.4 mU/kg X min) showed no additive effect on the inhibition of Ra. Ketones did not inhibit the insulin-stimulated metabolic clearance rate (MCR) for glucose. Infusion of somatostatin (0.2 micrograms/kg X min) initially decreased plasma glucose, Ra, and Rd, which was followed by an increase in plasma glucose and Ra; however, on infusion of somatostatin plus Na-DL-beta-OHB, hypoglycemia and the reduced Ra were maintained. In the anaesthetized 24-h starved miniature pig, Na-DL-beta-OHB infusion decreased the hepatic exchange for glucose, lactate, and FFA, whereas the exchange for glycerol, alanine, and alpha-amino-N as well as liver perfusion rate were unaffected. Simultaneously, portal glucagon and insulin as well as hepatic insulin extraction rate were elevated. Leg exchange for glucose, lactate, glycerol, alanine, alpha-amino-N, and FFA were decreased, while ketone body utilization increased. Repeated infusion of Na-DL-beta-OHB at the fourth, fifth, and sixth day of starvation in the conscious, unrestrained mini-pig resulted in a significant drop in urinary nitrogen (N)-excretion. However, this effect was mimicked by infusing equimolar amounts of Na-bicarbonate. In contrast, when only the ketoacid was given, urinary N-excretion accelerated. To summarize: (a) Ketone bodies decrease endogenous glucose production via an insulin-dependent mechanism; in addition, ketones probably exert a direct inhibitory action on gluconeogenesis. The ketone body-induced hypoalaninemia does not contribute to this effect. (b) The counterregulatory response to hypoglycemia is reduced by ketones. (c) As a consequence of the decrease in R(a), glucose utilization declines during ketone infusion. (d)The insulin-stimulated MCR for glucose is not affected by ketones. (e) Ketones in their physiological moiety do not show a protein-sparing effect.

Effect of starvation and refeeding on amino acid uptake by mammary gland of the lactating rat. Role of ketone bodies

Arteriovenous differences of amino acids across the mammary glands of lactating rats are diminished when the rats are starved for 24 h. When 24 h-starved rats were refed for 2 1/2 h, the arteriovenous differences of amino acids returned to values similar to those found in well-fed rats. In order to find a possible explanation for these rapid changes, we tested the effect of ketone bodies on amino acid uptake by the gland. At 5 min after injection of acetoacetate to fed rats, when the total concentration of ketone bodies in blood was similar to that found in starvation, the uptake of amino acids by the mammary gland was similar to that found after starvation, i.e. lower than in fed rats. However, 30 min after administration of acetoacetate, when the arterial concentration of ketone bodies had returned to values similar to those in fed rats, the arteriovenous differences of amino acids were similar to those found in fed rats. We conclude that the changes in blood ketone bodies may be responsible, at least in part, for the changes in amino acid uptake that occur in starvation and in the starvation--refeeding transition.

The human metabolic response to chronic ketosis without caloric restriction: physical and biochemical adaptation

To study the metabolic effects of ketosis without weight loss, nine lean men were fed a eucaloric balanced diet (EBD) for one week providing 35-50 kcal/kg/d, 1.75 g of protein per kilogram per day and the remaining kilocalories as two-thirds carbohydrate (CHO) and one-third fat. This was followed by four weeks of a eucaloric ketogenic diet (EKD)--isocaloric and isonitrogenous with the EBD but providing less than 20 g CHO daily. Both diets were appropriately supplemented with minerals and vitamins. Weight and whole-body potassium estimated by potassium-40 counting (40K) did not vary significantly during the five-week study. Nitrogen balance (N-Bal) was regained after one week of the EKD. The fasting blood glucose remained lower during the EKD than during the control diet (4.4 mmol/L at EBD, 4.1 mmol/L at EKD-4, P less than 0.01). The fasting whole-body glucose oxidation rate determined by a 13C-glucose primed constant infusion technique fell from 0.71 mg/kg/min during the control diet to 0.50 mg/kg/min (P less than 0.01) during the fourth week of the EKD. The mean serum cholesterol level rose (from 159 to 208 mg/dL) during the EKD, while triglycerides fell from 107 to 79 mg/dL. No disturbance of hepatic or renal function was noted at EKD-4. These findings indicate that the ketotic state induced by the EKD was well tolerated in lean subjects; nitrogen balance was regained after brief adaptation, serum lipids were not pathologically elevated, and blood glucose oxidation at rest was measurably reduced while the subjects remained euglycemic.

Effects of alpha-ketoisocaproate and of leucine on nitrogen metabolism in postoperative patients

21 patients undergoing major abdominal surgery were randomly assigned to one of three groups. On the day of surgery and for the succeeding 4 days each group received a daily infusion of one of the following: 10 g glucose plus 70 mmol NaHCO3, 70 mmol leucine plus 70 mmol NaHCO3, or 70 mmol of sodium alpha-ketoisocaproate (KIC). No other calories were given. Leucine infusions had no significant effect on nitrogen (N) balance, 3-methylhistidine excretion, or plasma concentrations of pre-albumin or retinol-binding protein, but they increased blood acetoacetate concentration (p = 0.004). N balance was less negative (p = 0.002) and 3-methylhistidine excretion lower (p = 0.002) in the group receiving KIC than in those receiving glucose. Blood ketone bodies, plasma prealbumin, and plasma retinol-binding protein concentrations at the end of the study were significantly higher in the KIC group than in the others. These N-sparing effects of KIC may be related to the heightened ketosis that followed its administration, to suppression of protein degradation, or to an effect on liver protein turnover. KIC alone in small doses diminishes N wastage in postoperative but under the same conditions leucine does not.

Body composition, energy expenditure, and plasma metabolites in long-term fasting geese

Starvation in 15 geese (mean initial body mass, m = 6.3 kg) fasting for about 40 days (mean decrease in m = 2.5 kg) was characterized by three periods. Period I (3-8 days), an adaptation period, was marked by a considerable decrease in the daily rate of change in m (dm) as well as in resting metabolic rate (RMR), and by high fat mobilization. In period II (a period of economy) the decreases in dm, RMR, and daily rate of nitrogen excretion (dne) were reduced: when expressed per unit of body mass these rates were either constant or decreased slightly. Period III, a critical period, was characterized by a rapid increase in both dm and dne that appeared when body mass had dropped to 4.7-3.2 kg. In parallel there was a greater decrease in intracellular fluid volume below 5 kg. Throughout the fast, in contrast to fasting mammals, plasma glucose and alanine concentrations were maintained at high levels (8-10 and 0.4 mM, respectively), and there was no increase in acetoacetate. However, after 20 days of fasting, plasma beta-hydroxybutyrate concentration (beta-OHB) increased to about 20 mM, while blood pH remained constant and blood PCO2 decreased. Thus, compensation for metabolic acidosis was partly attributed to respiratory alkalosis. Throughout the fast, the variations in beta-OHB were a mirror image of those for daily changes in body mass and in nitrogen excretion. This presumably reflects a hormonal change, but might also suggest a key role of beta-OHB in the control of energy expenditure and/or in regulation of body mass as well as in protein sparing.

Metabolic response to starvation. I. Relative effects of pregnancy and sex steroid administration in the rat

Increased sensitivity to a fast with rapid onset of ketosis, hypoalaninemia, and hypoglycemia is characteristic of rat and human gestation. The present study examines the role of sex steroids in the development of these metabolic changes. Subgroups of female rate received 10 microgram of estradiol (E), 10 mg of progesterone (P), or the two in combination (E + P) s.c. daily for 5 days. Control rats (C) received sesame oil alone. Different groups were starved 12, 24 and 48 hr during days 4 and 5 or treatment. Plasma substrate and insulin responses were measured and compared to results of similar studies performed on rats in late gestation. Administration of E or P along had no significant effects on measured parameters as compared to control values. However, the combined E + P regimen resulted in significantly higher ketonemia, greater hypoalaninemia, and relatively higher triglyceride concentrations than in control groups during fasting. Plasma triglyceride, free fatty acid, and ketone concentrations in the pregnant group exceeded values of both the E + P and control animals. However, plasma free fatty acids in the E + P group were significantly lower as compared to control values during starvation. These data suggest that the combined effects of estradiol and progesterone enhance ketogenesis and hypoalaninemia independent of the fetal-placental unit during starvation in pregnancy. Since the ketogenic effect was associated with a relative suppression of plasma free fatty acids, this may be indicative of a direct action of these hormones on hepatic disposition of free fatty acids and/or the biosynthetic pathways for ketone body production.