Ketosis In Rats Research Articles

Therapeutic ketosis with ketone ester delays central nervous system oxygen toxicity seizures in rats

Central nervous system oxygen toxicity (CNS-OT) seizures occur with little or no warning, and no effective mitigation strategy has been identified. Ketogenic diets (KD) elevate blood ketones and have successfully treated drug-resistant epilepsy. We hypothesized that a ketone ester given orally as R,S-1,3-butanediol acetoacetate diester (BD-AcAc(2)) would delay CNS-OT seizures in rats breathing hyperbaric oxygen (HBO(2)). Adult male rats (n = 60) were implanted with radiotelemetry units to measure electroencephalogram (EEG). One week postsurgery, rats were administered a single oral dose of BD-AcAc(2), 1,3-butanediol (BD), or water 30 min before being placed into a hyperbaric chamber and pressurized to 5 atmospheres absolute (ATA) O2. Latency to seizure (LS) was measured from the time maximum pressure was reached until the onset of increased EEG activity and tonic-clonic contractions. Blood was drawn at room pressure from an arterial catheter in an additional 18 animals that were administered the same compounds, and levels of glucose, pH, Po(2), Pco(2), β-hydroxybutyrate (BHB), acetoacetate (AcAc), and acetone were analyzed. BD-AcAc(2) caused a rapid (30 min) and sustained (>4 h) elevation of BHB (>3 mM) and AcAc (>3 mM), which exceeded values reported with a KD or starvation. BD-AcAc(2) increased LS by 574 ± 116% compared with control (water) and was due to the effect of AcAc and acetone but not BHB. BD produced ketosis in rats by elevating BHB (>5 mM), but AcAc and acetone remained low or undetectable. BD did not increase LS. In conclusion, acute oral administration of BD-AcAc(2) produced sustained ketosis and significantly delayed CNS-OT seizures by elevating AcAc and acetone.

A comparison of the effects on blood glucose and ketone-body levels, and of the toxicities, of pent-4-enoic acid and four simple fatty acids.

Abstract Some effects of the hypoglycaemic compound pent-4-enoic acid in rats and mice, are described. Pent-2-enoic acid, pentanoic acid, cyclopropanecarboxylic acid and cyclobutanecarboxylic acid, which were shown to be non-hypoglycaemic, were used as controls. Pent-4-enoic acid and cyclopropanecarboxylic acid caused ketosis in rats, with a lowering of the blood β-hydroxybutyrate/acetocetate (βHB/AcAc) ratio; some ketosis was caused by the other fatty acids but the βHB/AcAc ratio was not changed. Pent-4-enoic acid caused an increase in free fatty acid concentration in rat plasma. The acute toxicities of these compounds in mice were determined. The mechanism of the hypoglycaemic action of pent-4-enoic acid is discussed in relation to that of hypoglycin.

Induction of ketosis in rats fed low-carbohydrate, high-fat diets depends on the relative abundance of dietary fat and protein

Low-carbohydrate/high-fat diets (LC-HFDs) in rodent models have been implicated with both weight loss and as a therapeutic approach to treat neurological diseases. LC-HFDs are known to induce ketosis; however, systematic studies analyzing the impact of the macronutrient composition on ketosis induction and weight loss success are lacking. Male Wistar rats were pair-fed for 4 wk either a standard chow diet or one of three different LC-HFDs, which only differed in the relative abundance of fat and protein (percentages of fat/protein in dry matter: LC-75/10; LC-65/20; LC-55/30). We subsequently measured body composition by nuclear magnetic resonance (NMR), analyzed blood chemistry and urine acetone content, evaluated gene expression changes of key ketogenic and gluconeogenic genes, and measured energy expenditure (EE) and locomotor activity (LA) during the first 4 days and after 3 wk on the respective diets. Compared with chow, rats fed with LC-75/10, LC-65/20, and LC-55/30 gained significantly less body weight. Reductions in body weight were mainly due to lower lean body mass and paralleled by significantly increased fat mass. Levels of β-hydroxybutyate were significantly elevated feeding LC-75/10 and LC-65/20 but decreased in parallel to reductions in dietary fat. Acetone was about 16-fold higher with LC-75/10 only (P < 0.001). In contrast, rats fed with LC-55/30 were not ketotic. Serum fibroblast growth factor-21, hepatic mRNA expression of hydroxymethylglutaryl-CoA-lyase, peroxisome proliferator-activated receptor-γ coactivator-1α, and peroxisome proliferator-activated receptor-γ coactivator-1β were increased with LC-75/10 only. Expression of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase was downregulated by 50-70% in LC-HF groups. Furthermore, EE and LA were significantly decreased in all groups fed with LC-HFDs after 3 wk on the diets. In rats, the absence of dietary carbohydrates per se does not induce ketosis. LC-HFDs must be high in fat, but also low in protein contents to be clearly ketogenic. Independent of the macronutrient composition, LC-HFD-induced weight loss is not due to increased EE and LA.

Sodium Pivalate Treatment Reduces Tissue Carnitines and Enhances Ketosis in Rats

Sodium pivalate, a compound conjugated to carnitine and excreted in the urine was used to induce a secondary carnitine deficiency. In the first series of experiments, rats received in their drinking water either 20 mmol/L sodium pivalate (experimental) or 20 mmol/L sodium bicarbonate (control) for 4 d, 2 wk, or 8 wk. Tissues and urine were collected, and carnitine concentrations in liver, skeletal muscle, heart, plasma and urine were determined. The total carnitine concentrations in tissues and plasma of pivalate-treated rats were significantly depressed (P less than 0.05) at all time points, except at 4 d for skeletal muscle and at 4 d and 2 wk for liver. The acylcarnitine:free carnitine ratios in urine and plasma of the pivalate-treated animals were significantly higher at all time points relative to the controls. In the second experiment, rats received either the pivalate or the bicarbonate treatments for 15 d followed by a 2-d fast. After fasting, the plasma beta-hydroxybutyrate of pivalate-treated rats was significantly higher relative to controls, but there was no significant difference in plasma glucose concentrations. The reduced plasma and tissue carnitine concentrations, increased acylcarnitine:free carnitine ratio in plasma and urine, and fasting ketosis found in pivalate-treated rats are findings also reported for human secondary carnitine deficiency due to organic acidurias.

Metabolites and ketone body production following methyl n-butyl ketone exposure as possible indices of MnBK potentiation of carbon tetrachloride hepatotoxicity

While the biotransformation of methyl n-butyl ketone (MnBK) in animals is well characterized, little is known about the quantitative relationship between hepatic and plasma MnBK concentrations. This study provides such information and emphasizes the usefulness of MnBK metabolite quantification, as well as MnBK-induced metabolic ketosis for the biological monitoring of MnBK exposure in rats. Elimination of MnBK was followed 24 hr after oral administration (0.95, 1.90, and 5.70 mmol/kg in corn oil) to male Sprague-Dawley rats. Two metabolites [2-hexanol (2HOL), and 2,5-hexanedione (2.5HD)] were also monitored and their kinetics determined. These data were compared to ketone body (KB) concentrations found in plasma and liver during the same period. Plasma concentrations of MnBK and 2,5HD correlated well with those in the liver. This was not the case for 2HOL. MnBK, 2HOL, and 2,5HD were no longer detected in plasma and liver 18 hr after dosing. Meanwhile, a marked ketosis was observed from 12 to 24 hr. This ketotic state was due to an increase in β-hydroxybutyrate (BOHB), while acetoacetate remained at its basal levels. These data indicate that MnBK can induce ketosis in rats and suggest that the resulting BOHB might be used as an alternative biological monitor of MnBK exposures at high concentrations.

C6-C10-dicarboxylic aciduria: biochemical considerations in relation to diagnosis of beta-oxidation defects.

By means of gas chromatographic methods substantial amounts of the C6-C10-dicarboxylic acids, i.e. adipic, suberic and sebacic acids, have been found in the urine from children with unexplained attacks of lethargy and hypotonia, presumably related to episodes of fever and/or insufficient food intake. The course have once been fatal and is often characterized by severe hypoglycemia without ketonuria. Systematic gas chromatographic/mass spectrometric determinations of selected organic acid metabolites in the urine, together with enzymatic measurements in fibroblasts and clinical data from 4 patients of this category, have shown that the biochemical basis of this syndrome can be inborn errors of the beta-oxidation of fatty acids, localized to the medium-chain acyl-CoA dehydrogenation system. The biosynthesis of adipic, suberic and sebacic acids was studied using ketotic rats as the model, since ketosis in rats and humans is accompanied by excessive urinary excretion of adipic and suberic acids. A probable pathway for the production of the three dicarboxylic acids was found to be an initial omega-oxidation of the medium-chain C10-C14-monocarboxylic acids followed by beta-oxidation of the resulting medium-chain dicarboxylic acids. It is argued that the source of the omega-oxidizable monocarboxylic acids in ketosis most probably is the fat deposites, and it is speculated that the patients with beta-oxidation defects supplement this source with beta-oxidation intermediate medium-chain monocarboxylic acids, accumulated as a result of the defect. The ratio between the excreted amounts of adipic acid and sebacic acid in the urine from the patients with beta-oxidation defects is less than 50. This is in contrast to the ratio in urine from ketotic patients, where it is greater than 100. Adipic acid/sebacic acid ratio-measured by means of a gas chromatographic analysis-is therefore suggested as a tool in the diagnosis of dicarboxylic acidurias. Based on the clinical picture and the pattern of a series of organic acids in the urinary metabolic profile our four patients can be divided in two types of dicarboxylic aciduria. The two types have different therapeutic implications.

Ketogenesis in vitro

Starvation for 48 h and diabetes (induced either by alloxan treatment or by pancreatectomy) resulted in increasing degrees of ketosis in rats. Optimal conditions were established for acetoacetate synthesis from CoASAc in homogenates of liver taken from animals of all experimental groups. The results obtained from these studies show that the dramatic increase in ketosis associated with starvation and diabetes cannot be accounted for by the minor fluctuations observed in the levels of hepatic enzymes responsible for ketogenesis.

THE RELATION OF THE PITUITARY TO BLOOD LIPIDS1

BRUN AND LING (I, 2) and Anselmino and Hoffman (3) demonstrated that B(URN)extracts(AND)of the anterior pituitary produced a ketosis in rats or rabbits which were fasting or receiving a high fat diet. That this effect was not mediated through the thyroid was indicated by Funk (4) who observed that thyroidectomizjed rats responded to AP extracts similar to normal animals and further Butts, Cutler and Deuel (5) reported little ketonuria following injections of the thyrotropic hormone. On the other hand, MacKay and Barnes (6) and Fry (7) report a lack of ketosis in adrenalectomised rats injected with a ketogenic AP extract. Mirsky (8) concluded that the adrenal gland by itself is not essential for the ketogenic activity of extracts of the AP, but rather an increase in the renal threshold for ketone bodies is responsible for the decreased ketonuria.