Both uridine and exogenous ketone supplements decreased the number of spike-wave discharges (SWDs) in a rat model of human absence epilepsy Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. It has been suggested that alleviating influence of both uridine and ketone supplements on absence epileptic activity may be modulated by A₁ type adenosine receptors (A₁Rs). The first aim was to determine whether intraperitoneal (i.p.) administration of a specific A₁R antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX; 0.2 mg/kg) and a selective adenosine A_2A receptor antagonist (7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo [1,5-c]pyrimidine) (SCH 58261; 0.5 mg/kg) have a modulatory influence on i.p. 1000 mg/kg uridine-evoked effects on SWD number in WAG/Rij rats. The second aim was to assess efficacy of a sub-effective dose of uridine (i.p. 250 mg/kg) combined with beta-hydroxybutyrate salt + medium chain triglyceride (KSMCT; 2.5 g/kg, gavage) on absence epilepsy. DPCPX completely abolished the i.p. 1000 mg/kg uridine-evoked alleviating effect on SWD number whereas SCH 58261 was ineffective, confirming the A₁R mechanism. Moreover, the sub-effective dose of uridine markedly enhanced the effect of KSMCT (2.5 g/kg, gavage) on absence epileptic activity. These results demonstrate the anti-epilepsy benefits of co-administrating uridine and exogenous ketone supplements as a means to treat absence epilepsy.

While one-third of the population can be affected by anxiety disorders during their lifetime, our knowledge of the pathophysiology of these disorders is far from complete. Previously, it has been demonstrated in male animals that exogenous ketone supplement-evoked ketosis can decrease anxiety levels in preclinical rodent models, such as Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. Thus, in this study, we investigated whether intragastric gavage of the exogenous ketone supplement KEMCT (mix of 1,3-butanediol-acetoacetate diester/ketone ester/KE and medium-chain triglyceride/MCT oil in 1:1 ratio) for 7 days can alter the anxiety levels of female WAG/Rij rats using the light–dark box (LDB) test. We demonstrated that a lower dose of KEMCT (3 g/kg/day) increased blood R-βHB (R-β-hydroxybutyrate) levels and significantly decreased anxiety levels (e.g., increased the time spent in the light compartment) in female WAG/Rij rats on the seventh day of administration. Although the higher KEMCT dose (5 g/kg/day) increased blood R-βHB levels more effectively, compared with the lower KEMCT dose, anxiety levels did not improve significantly. We conclude that ketone supplementation might be an effective strategy to induce anxiolytic effects not only in male but also in female WAG/Rij rats. However, these results suggest that the optimal level may be moderately, not highly, elevated blood R-βHB levels when the goal is to alleviate symptoms of anxiety. More studies are needed to understand the exact mechanism of action of ketone supplementation on anxiety levels and to investigate their use in other animal models and humans for the treatment of anxiety disorders and other mental health conditions.

Approximately 30% of patients with epilepsy are drug-refractory. There is an urgent need to elucidate the exact pathophysiology of different types of epilepsies and the mechanisms of action of both antiseizure medication and metabolic therapies to treat patients more effectively and safely. For example, it has been demonstrated that exogenous ketone supplement (EKS)-generated therapeutic ketosis, as a metabolic therapy, may decrease epileptic activity in both animal models and humans, but its exact mechanism of action is unknown. However, it was demonstrated that therapeutic ketosis, among others, can increase adenosine level, which may enhance activity of A1 adenosine receptors (A₁Rs) in the brain. It has also been demonstrated previously that adenosine has anti-epileptic effect through A₁Rs in different models of epilepsies. Thus, it is possible that (i) therapeutic ketosis generated by the administration of EKSs may exert its anti-epileptic effect through, among other mechanisms, increased adenosine level and A₁R activity and that (ii) the enhanced activity of A₁Rs may be a necessary anti-epileptic mechanism evoked by EKS administration-generated ketosis. Moreover, EKSs can evoke and maintain ketosis without severe side effects. These results also suggest that the therapeutic application of EKS-generated ketosis may be a promising opportunity to treat different types of epilepsies. In this literature review, we specifically focus on the putative role of A₁Rs in the anti-epileptic effect of EKS-induced ketosis.

It has been demonstrated that isoflurane-induced anesthesia can increase the blood glucose level, leading to hyperglycemia and several adverse effects. The administration of a mix of ketone diester (KE) and medium-chain triglyceride (MCT) oil, named KEMCT, abolished the isoflurane-anesthesia-induced increase in blood glucose level and prolonged the recovery time from isoflurane anesthesia in a male preclinical rodent model, Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. While most preclinical studies use exclusively male animals, our previous study on blood glucose changes in response to KEMCT administration showed that the results can be sex-dependent. Thus, in this study, we investigated female WAG/Rij rats, whether KEMCT gavage (3 g/kg/day for 7 days) can change the isoflurane (3%)-anesthesia-induced increase in blood glucose level and the recovery time from isoflurane-evoked anesthesia using the righting reflex. Moreover, KEMCT-induced ketosis may enhance both the extracellular level of adenosine and the activity of adenosine A1 receptors (A1Rs). To obtain information on the putative A1R mechanism of action, the effects of an A1R antagonist, DPCPX (1,3-dipropyl-8-cyclopentylxanthine; intraperitoneal/i.p. 0.2 mg/kg), on KEMCT-generated influences were also investigated. Our results show that KEMCT supplementation abolished the isoflurane-anesthesia-induced increase in blood glucose level, and this was abrogated by the co-administration of DPCPX. Nevertheless, KEMCT gavage did not change the recovery time from isoflurane-induced anesthesia. We can conclude that intragastric gavage of exogenous ketone supplements (EKSs), such as KEMCT, can abolish the isoflurane-anesthesia-induced increase in blood glucose level in both sexes likely through A1Rs in WAG/Rij rats, while recovery time was not affected in females, unlike in males. These results suggest that the administration of EKSs as an adjuvant therapy may be effective in mitigating metabolic side effects of isoflurane, such as hyperglycemia, in both sexes.

Background: It has been demonstrated that levetiracetam can decrease absence epileptic activity in both human patients and different types of animal models of absence epilepsy, such as the genetically absence epileptic Wistar Albino Glaxo/Rijswijk (WAG/Rij) rat. It was also suggested previously that exogenous ketone supplements (EKSs)-evoked ketosis not only decreases the number of spike-wave discharges (SWDs) but also enhances the anti-absence epileptic effect of pyrimidine nucleoside uridine in WAG/Rij rats. These findings suggest that EKSs may enhance the efficacy of clinically used anti-epileptic drugs, such as levetiracetam. Methods: We investigated the effect of not only levetiracetam (intraperitoneal/i.p. 200 mg/kg) alone and KEKS supplemented food (containing 10% ketone ester/KE and 10% ketone salt/KS in a normal rat chow) alone, but also the combination of levetiracetam and KEKS supplemented food on SWD number and SWD time for 5 days in WAG/Rij rats. For evaluation of SWDs, electroencephalographic (EEG) recordings were performed every day. Moreover, for the measurement of blood glucose and R-beta-hydroxybutyrate (R-βHB) levels, the blood was taken from the tail vein of rats after EEG registration. Results: It was demonstrated that the administration of both levetiracetam alone and KEKS food alone decreased the SWD number and time spent in SWD, compared to control. Moreover, after combined administration of levetiracetam with KEKS food, enhanced anti-absence epileptic effect was observed, compared to levetiracetam alone. Blood R-βHB level significantly increased after administration of both KEKS food alone and KEKS food in combination with levetiracetam. Nevertheless, these treatments did not significantly change the blood glucose levels. Conclusions: We can conclude that EKSs may be able to enhance the anti-epileptic effect of different drugs, and this combined treatment method may represent a promising new approach and effective therapy against epileptic seizures, especially in treatment-resistant patients.

Background/Objectives: Inflammatory processes, including elevated pro-inflammatory cytokines such as interleukin 1β (IL-1β), have been implicated in the pathophysiology of anxiety disorders. The ketone body β-hydroxybutyrate (βHB) was shown to mitigate inflammatory processes induced by lipopolysaccharide (LPS) administration. It was also suggested that exogenous ketone supplements, such as ketone esters (KEs) and ketone salts (KSs), can decrease anxiogenic effects through increased blood ketone levels in the body (ketosis) in preclinical animal models. Methods: Thus, we investigated whether standard rodent food supplemented with KEKS (KEKS food: mix of a KE R/S-1,3-butanediol-acetoacetate diester and a KS Na⁺- and Ca²⁺- R/S-βHB salt in 1:1 ratio) for 7 days can alleviate the intraperitoneal (i.p.) 1 mg/kg LPS-generated anxiogenic effect in female Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. For the evaluation of anxiogenic effects, the light–dark box (LDB) test was used. Results: KEKS food significantly increased the blood R-β-hydroxybutyrate (R-βHB) level and decreased the blood glucose level compared to the baseline. Moreover, the LPS significantly (i) decreased the time spent in the light compartment, the number of chamber transitions, the number of re-entries to the light compartment and the number of rearing in the light compartment, and also (ii) increased the time of latency to the first re-entry to the light compartment compared to control. Nevertheless, KEKS food treatment abolished LPS-generated anxiety-like behavior. Conclusions: The current study demonstrated that a 7-day KEKS-supplemented diet can increase blood R-βHB levels and abolish acute LPS administration-evoked increases in anxiety levels in female WAG/Rij rats. Moreover, our results support the important role of neuroinflammation in pathological processes resulting in anxiety. Thus, these results suggest that exogenous ketone supplement-generated ketosis may be a promising therapeutic tool in the treatment of inflammatory process-mediated diseases, such as anxiety disorders.