Proton and electric charge translocation in mitochondrial energy transduction

Revealing Alteration in the Hepatic Glucose Metabolism of Genetically Improved Carp, Jayanti Rohu Labeo rohita Fed a High Carbohydrate Diet Using Transcriptome Sequencing

Although feed cost is the greatest concern in aquaculture, the inclusion of carbohydrates in the fish diet, and their assimilation, are still not well understood in aquaculture species. We identified molecular events that occur due to the inclusion of high carbohydrate levels in the diets of genetically improved 'Jayanti rohu' Labeo rohita. To reveal transcriptional changes in the liver of rohu, a feeding experiment was conducted with three doses of gelatinized starch (20% (control), 40%, and 60%). Transcriptome sequencing revealed totals of 15,232 (4464 up- and 4343 down-regulated) and 15,360 (4478 up- and 4171 down-regulated) differentially expressed genes. Up-regulated transcripts associated with glucose metabolisms, such as hexokinase, PHK, glycogen synthase and PGK, were found in fish fed diets with high starch levels. Interestingly, a de novo lipogenesis mechanism was found to be enriched in the livers of treated fish due to up-regulated transcripts such as FAS, ACCα, and PPARγ. The insulin signaling pathways with enriched PPAR and mTOR were identified by Kyoto Encyclopedia of Genes and Genome (KEGG) as a result of high carbohydrates. This work revealed for the first time the atypical regulation transcripts associated with glucose metabolism and lipogenesis in the livers of Jayanti rohu due to the inclusion of high carbohydrate levels in the diet. This study also encourages the exploration of early nutritional programming for enhancing glucose efficiency in carp species, for sustainable and cost-effective aquaculture production.

Mitochondrial Ultrastructure and Glucose Signaling Pathways Attributed to the Kv1.3 Ion Channel

Gene-targeted deletion of the potassium channel Kv1.3 (Kv1.3^−∕−) results in “Super-smeller” mice with a sensory phenotype that includes an increased olfactory ability linked to changes in olfactory circuitry, increased abundance of olfactory cilia, and increased expression of odorant receptors and the G-protein, G_olf. Kv1.3^−∕− mice also have a metabolic phenotype including lower body weight and decreased adiposity, increased total energy expenditure (TEE), increased locomotor activity, and resistance to both diet- and genetic-induced obesity. We explored two cellular aspects to elucidate the mechanism by which loss of Kv1.3 channel in the olfactory bulb (OB) may enhance glucose utilization and metabolic rate. First, using in situ hybridization we find that Kv1.3 and the insulin-dependent glucose transporter type 4 (GLUT4) are co-localized to the mitral cell layer of the OB. Disruption of Kv1.3 conduction via construction of a pore mutation (W386F Kv1.3) was sufficient to independently translocate GLUT4 to the plasma membrane in HEK 293 cells. Because olfactory sensory perception and the maintenance of action potential (AP) firing frequency by mitral cells of the OB is highly energy demanding and Kv1.3 is also expressed in mitochondria, we next explored the structure of this organelle in mitral cells. We challenged wildtype (WT) and Kv1.3^−∕− male mice with a moderately high-fat diet (MHF, 31.8 % kcal fat) for 4 months and then examined OB ultrastructure using transmission electron microscopy. In WT mice, mitochondria were significantly enlarged following diet-induced obesity (DIO) and there were fewer mitochondria, likely due to mitophagy. Interestingly, mitochondria were significantly smaller in Kv1.3^−∕− mice compared with that of WT mice. Similar to their metabolic resistance to DIO, the Kv1.3^−∕− mice had unchanged mitochondria in terms of cross sectional area and abundance following a challenge with modified diet. We are very interested to understand how targeted disruption of the Kv1.3 channel in the OB can modify TEE. Our study demonstrates that Kv1.3 regulates mitochondrial structure and alters glucose utilization; two important metabolic changes that could drive whole system changes in metabolism initiated at the OB.

Cryopreservation of zebrafish (Danio rerio) oocytes using improved controlled slow cooling protocols

Cryopreservation of gametes provides a promising method to preserve fish genetic material. Previously we reported some preliminary results on cryopreservation of zebrafish (Danio rerio) oocytes using controlled slow cooling and determined the optimum cryoprotective medium and cooling rate for stage III zebrafish oocytes. In the present study, the effects of two different cryopreservation media, cryoprotectant removal method, final sample freezing temperature before LN(2) plunge, warming rate, and the post-thaw incubation time on oocyte viability were investigated. Commonly used cryoprotectant methanol and glucose were used in this study. Stage III zebrafish oocytes were frozen in standard culture medium 50% L-15 or in a sodium-free KCl buffer medium. Oocyte viability was assessed using trypan blue staining and ATP assay. The viability of oocytes frozen in KCl buffer was significantly higher than oocytes frozen in L-15 medium. The results also showed that fast thawing and stepwise removal of cryoprotectant improved oocyte survival significantly, with highest viability of 88.0+/-1.7% being obtained immediately after rapid thawing when assessed by trypan blue staining. However, after 2h incubation at 22 degrees C the viability of freeze-thawed oocytes decreased to 29.5+/-5.1%. Results also showed that the ATP level in oocytes decreased significantly immediately after thawing. All oocytes became translucent after freezing which complicated the use of GVBD test (in vitro maturation of oocytes followed by observation of germinal vesicle breakdown which results in oocytes becoming translucent). New oocyte viability assessment methods are urgently needed.