Ketogenic diet feeding improves aerobic metabolism property in extensor digitorum longus muscle of sedentary male rats.

Recent studies of the ketogenic diet, an extremely high-fat diet with extremely low carbohydrates, suggest that it changes the energy metabolism properties of skeletal muscle. However, ketogenic diet effects on muscle metabolic characteristics are diverse and sometimes countervailing. Furthermore, ketogenic diet effects on skeletal muscle performance are unknown. After male Wistar rats (8 weeks of age) were assigned randomly to a control group (CON) and a ketogenic diet group (KD), they were fed for 4 weeks respectively with a control diet (10% fat, 10% protein, 80% carbohydrate) and a ketogenic diet (90% fat, 10% protein, 0% carbohydrate). After the 4-week feeding period, the extensor digitorum longus (EDL) muscle was evaluated ex vivo for twitch force, tetanic force, and fatigue. We also analyzed the myosin heavy chain composition, protein expression of metabolic enzymes and regulatory factors, and citrate synthase activity. No significant difference was found between CON and KD in twitch or tetanic forces or muscle fatigue. However, the KD citrate synthase activity and the protein expression of Sema3A, citrate synthase, succinate dehydrogenase, cytochrome c oxidase subunit 4, and 3-hydroxyacyl-CoA dehydrogenase were significantly higher than those of CON. Moreover, a myosin heavy chain shift occurred from type IIb to IIx in KD. These results demonstrated that the 4-week ketogenic diet improves skeletal muscle aerobic capacity without obstructing muscle contractile function in sedentary male rats and suggest involvement of Sema3A in the myosin heavy chain shift of EDL muscle.

Ketogenic diet does not impair spatial ability controlled by the hippocampus in male rats.

A ketogenic diet was recently shown to reduce glutamate accumulation in synaptic vesicles, decreasing glutamate transmission. We questioned whether a ketogenic diet affects hippocampal function, as glutamate transmission is critically involved in visuospatial ability. In the present study, male Wistar rats were maintained on a ketogenic diet containing 10% protein and 90% fat with complements for 3 weeks to change their energy expenditure from glucose-dependent to fat-dependent. Control rats were fed a diet containing 10% protein, 10% fat, and 80% carbohydrates. The fat-dependent energy expenditure induced by the ketogenic diet led to decreased body weight and increased blood ketone production, though the rats in the two groups consumed the same number of calories. The ketogenic diet did not alter food preferences for the control or high-fat diet containing 10% protein, 45% fat, and 45% carbohydrates. Anxiety in the open field was not altered by ingestion the ketogenic diet. However, rats fed the ketogenic diet performed better in the Y-maze test than rats fed the control diet. No difference was observed between the two groups in the Morris water maze test. Finally, Western blot revealed that the hippocampal expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptor subunit 1 (GluR1) was significantly increased in mice fed a ketogenic diet. These results suggest that hippocampal function is not impaired by a ketogenic diet and we speculate that the fat-dependent energy expenditure does not impair visuospatial ability.

Immunohistochemical evidence for the relationship between microglia and GnRH neurons in the preoptic area of ovariectomized rats with and without steroid replacement.

Prostaglandins (PGs), whose synthesis is catalyzed by the rate-limiting enzyme cyclooxygenase (COX) including COX-1 and COX-2, are among the important mediators involved in the regulation of gonadotropin-releasing hormone (GnRH) secretion. However, the cellular origin of PGs remains obscure in terms of its relationship to GnRH neurons. The present study was therefore aimed to clarify the anatomical relationship between COX-1-producing microglia and GnRH neurons in the preoptic area (POA), and to examine possible influence of ovarian steroids. We performed a triple labeled immunofluorescent histochemistry of COX-1, CD11b (a specific marker for microglia) and GnRH in the POA of ovarian steroid-primed and non-primed ovariectomized rats. The result confirmed our previous study suggesting COX-1 immunoreactivity in the vicinity of, but not within, GnRH neurons in the POA. COX-1 around GnRH cells was entirely (100%) localized in cells containing CD11b regardless of steroid replacement in ovariectomized rats. These CD11b-immunoreactive cells had small cell bodies and highly branched fibers characteristic of ramified microglia. Three-dimensional reconstruction of confocal images revealed close proximity of some COX-1-containing microglia and GnRH neurons. These results showed selective and constitutive expression of COX-1 in ramified microglia in the vicinity of GnRH neurons, providing evidence for intercellular communication, mediated by PGs, from microglia to GnRH cells.

Single bout of running exercise changes LC3-II expression in rat cardiac muscle.

Macroautophagy (autophagy) is an intracellular catalytic process. We examined the effect of running exercise, which stimulates cardiac work physiologically, on the expression of microtubule-associated protein 1 light chain 3 (LC3)-II, an indicator of autophagy, as well as some autophagy-related proteins in rat cardiac muscle. The left ventricles were taken from rats immediately (0 h), and at 0.5h, 1h or 3h after a single bout of running exercise on a treadmill for 30 min and also from rats in a rest condition. In these samples, we evaluated the level of LC3-II and p62, and the phosphorylation level of mammalian target of rapamycin (mTOR), Akt and AMP-activated protein kinase alpha (AMPKα) by Western blotting. The exercise produced a biphasic change in LC3-II, with an initial decrease observed immediately after the exercise and a subsequent increase 1h thereafter. LC3-II then returned to the rest level at 3h after the exercise. A negative correlation was found between the LC3-II expression and mTOR phosphorylation, which plays a role in inhibiting autophagy. The exercise increased phosphorylation of AMPKα, which stimulates autophagy via suppression of mTOR phosphorylation, immediately after exercise. The level of p62 and phosphorylated Akt was not altered significantly by the exercise. These results suggest for the first time that a single bout of running exercise induces a biphasic change in autophagy in the cardiac muscle. The exercise-induced change in autophagy might be partially mediated by mTOR in the cardiac muscle.