Search results
Found 12032 matches for
Prior ingestion of exogenous ketone monoester attenuates the glycaemic response to an oral glucose tolerance test in healthy young individuals.
KEY POINTS: The recent development of exogenous ketone supplements allows direct testing of the metabolic effects of elevated blood ketones without the confounding influence of widespread changes experienced with ketogenic diets or prolonged fasting. In the present study, we determined the effect of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate ketone monoester on the glycaemic response and insulin sensitivity index during a 2 h oral glucose tolerance test (OGTT) in humans. The results obtained show that consuming a ketone monoester supplement 30 min prior to an OGTT reduced the glycaemic response and markers of insulin sensitivity without affecting insulin secretion. The findings of the present study provides evidence that ketone supplements could have therapeutic potential for future application as a glucose-lowering nutritional supplement. ABSTRACT: The main objectives of the present study were: (i) to determine whether acute ingestion of ketone monoester (Kme ); (R)-3-hydroxybutyl (R)-3-hydroxybutyrate impacts plasma glucose levels during a standardized oral glucose tolerance test (OGTT) and (ii) to compare changes in insulin concentrations and estimates of insulin sensitivity after acute Kme supplementation. Twenty healthy participants (n = 10 males/females) aged between 18 and 35 years took part in a randomized cross-over study. After an overnight fast, participants consumed a Kme supplement (ΔG®; TΔS Ltd, UK, Oxford, UK; 0.45 ml kg-1 body weight) or placebo (water) 30 min before completing a 75 g OGTT. Blood samples were collected every 15-30 min over 2.5 h. The participants and study personnel performing the laboratory analyses were blinded to the study condition. Kme acutely raised blood d-beta-hydroxybutyrate (β-OHB) to 3.2 ± 0.6 mm within 30 min with levels remaining elevated throughout the entire OGTT. Compared to placebo, Kme significantly decreased the glucose area under the curve (AUC; -17%, P = 0.001), non-esterified fatty acid AUC (-44%, P < 0.001) and C-peptide incremental AUC (P = 0.005), at the same time as improving oral glucose insulin sensitivity index by ∼11% (P = 0.001). In conclusion, a Kme supplement that acutely increased β-OHB levels up to ∼3 mm attenuated the glycaemic response to an OGTT in healthy humans. The reduction in glycaemic response did not appear to be driven by an increase in insulin secretion, although it was accompanied by improved markers of insulin sensitivity. These results suggest that ketone monoester supplements could have therapeutic potential in the management and prevention of metabolic diseases.
The Importance of Calcium Ions for Determining Mitochondrial Glycerol-3-Phosphate Dehydrogenase Activity When Measuring Uncoupling Protein 1 (UCP1) Function in Mitochondria Isolated from Brown Adipose Tissue.
Glycerol-3-phosphate is an excellent substrate for FAD-linked mitochondrial glycerol-3-phosphate dehydrogenase (mGPDH) in brown adipose tissue mitochondria and is regularly used as the primary substrate to measure oxygen consumption and reactive oxygen consumption by these mitochondria. mGPDH converts cytosolic glycerol-3-phosphate to dihydroxyacetone phosphate, feeding electrons directly from the cytosolic side of the mitochondrial inner membrane to the CoQ-pool within the inner membrane. mGPDH activity is allosterically activated by calcium, and when calcium chelators are present in the mitochondrial preparation medium and/or experimental incubation medium, calcium must be added to insure maximal mGPDH activity. It was demonstrated that in isolated brown adipose tissue mitochondria (1) mGPDH enzyme activity is maximal at free calcium ion concentrations in the 350 nM-1 μM range, (2) that ROS production also peaks in the 10-100 nM range in the presence of a UCP1 inhibitory ligand (GDP) but wanes with further increasing calcium concentration, and (3) that oxygen consumption rates peak in the 10-100 nM range with rates being maintained at higher calcium concentrations. This article provides easy-to-follow protocols to facilitate the measurement of mGPDH-dependent UCP1 activity in the presence of calcium for isolated brown adipose tissue mitochondria.
Oral 28-day and developmental toxicity studies of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate.
(R)-3-Hydroxybutyl (R)-3-hydroxybutyrate (ketone monoester) has been developed as an oral source of ketones, which may be utilized for energy. In a 28-day toxicity study, Crl:WI (Wistar) rats received diets containing, as 30% of the calories, ketone monoester (12 and 15 g/kg body weight/day for male and female rats, respectively). Control groups received either carbohydrate- or fat-based diets. Rats in the test group consumed less feed and gained less weight than control animals; similar findings have been documented in studies of ketogenic diets. Between-group differences were noted in selected hematology, coagulation, and serum chemistry parameters; however, values were within normal physiological ranges and/or were not accompanied by other changes indicative of toxicity. Upon gross and microscopic evaluation, there were no findings associated with the ketone monoester. In a developmental toxicity study, pregnant Crl:WI (Han) rats were administered 2g/kg body weight/day ketone monoester or water (control) via gavage on days 6 through 20 of gestation. No Caesarean-sectioning or litter parameters were affected by the test article. The overall incidence of fetal alterations was higher in the test group; however, there were no specific alterations attributable to the test substance. The results of these studies support the safety of ketone monoester.
Gastrointestinal Effects of Exogenous Ketone Drinks are Infrequent, Mild and Vary According to Ketone Compound and Dose.
Exogenous ketone drinks may improve athletic performance and recovery, but information on their gastrointestinal (GI) tolerability is limited. Studies to date have used simplistic reporting methodology that inadequately represents symptom type, frequency and severity. Here, GI symptoms were recorded during three studies of exogenous ketone monoester (KME) and salt (KS) drinks. Study 1 compared low and high dose KME and KS drinks consumed at rest. Study 2 compared KME to isocaloric carbohydrate (CHO) consumed at rest either when fasted or after a standard meal. Study 3 compared KME+CHO to isocaloric CHO consumed before and during 3.25h of bicycle exercise. Participants reported symptom type and rated severity be-tween 0-8 using a Likert Scale at regular intervals. The number of visits with no symptoms reported after ketone drinks was n=32/60 in Study 1, n=9/32 in Study 2 and n=20/42 in Study 3. Following KME and KS drinks, symptoms were acute but mild and were fully resolved by the end of the study. High dose KS drinks caused greater total-visit symptom load than low dose KS (13.8±4.3 vs. 2.0±1.0; P<0.05) and significantly greater time-point symptom load than KME drinks 1-2h post-drink. At rest, KME drinks caused greater total-visit symptom load than CHO drinks (5.0±1.6 vs. 0.6±0.4; P<0.05). However, during exercise there was no significant difference in total-visit symptom load between KME+CHO (4.2±1.0) and CHO (7.2±1.9) drinks. In summary, exogenous ketone drinks cause mild GI symptoms that depend on time, the type and amount of compound consumed and on exercise.
Data on uncoupling protein-3 levels, hypoxia, low flow ischemia, and insulin stimulation in dystrophin-deficient mdx mouse hearts.
The data contain body weights, plasma free fatty acids concentrations and cardiac uncoupling protein-3 protein levels for wild-type and mdx mice. The data provide heart rates, left ventricular contractile functions, coronary flow, phosphocreatine concentrations, and adenosine 5'-triphosphate (ATP) concentrations throughout hypoxia in mdx mouse hearts. This data article also provides left ventricular contractile functions after low flow ischemia with and without glucose, glycogen levels before ischemia or hypoxia, glucose uptake rates during low flow ischemia and insulin stimulation, and insulin-stimulated phospho-Akt protein levels, a protein in insulin signaling, in mdx mouse hearts.
Data on triiodothyronine treated peroxisome proliferator-activated receptor-alpha-null mouse hearts using magnetic resonance imaging and magnetic resonance spectroscopy.
This data contain left ventricular end-diastolic volumes, end-systolic volumes, stroke volumes, ejection fractions, cardiac outputs, heart rates, phosphocreatine concentrations, adenosine 5'-triphosphate (ATP) concentrations, total creatine concentrations, citrate synthase activities and heart weights for wild-type and peroxisome proliferator-activated receptor-alpha-null mouse hearts without and with triiodothyronine treatment.
Recent advances in image-based stem-cell labeling and tracking, and scaffold-based organ development in cardiovascular disease
© 2014 Bentham Science Publishers. Myocardial infarction (MI)and heart failure (HF)are leading causes of mortality and morbidity in the Western World. Therapeutic approaches using interventional cardiology and bioengineering techniques have thus far focused on either salvaging viable tissue post-infarction or preserving cardiac function in the failing myocardium. Regenerative medicine on the other hand, attempts to renew damaged tissue and enhance cardiac functional performance. Tremendous advances have been made in this field since the introduction and ethical approval for use of stem-cells (SC)and relevant technologies in pre-clinical and clinical practice. While study outcomes are still ambivalent on the potential translational impact of SCs, renewed hope has arisen since the introduction of induced pluripotent stem-cells (iPS)and the prospect of intact organ development and transplantation. The aim of this work is to review recent discoveries and the patent landscape employing stem-cell engineering, labeling and image-based monitoring strategies, their use in bioreactors and constructions of enriched bio-artificial membranes, as well as the potential role in artificial organ development and transplantation, with relevance to anticipated impact in pre-clinical screening and widespread clinical use.
Binary Switching of Calendar Cells in the Pituitary Defines the Phase of the Circannual Cycle in Mammals.
Persistent free-running circannual (approximately year-long) rhythms have evolved in animals to regulate hormone cycles, drive metabolic rhythms (including hibernation), and time annual reproduction. Recent studies have defined the photoperiodic input to this rhythm, wherein melatonin acts on thyrotroph cells of the pituitary pars tuberalis (PT), leading to seasonal changes in the control of thyroid hormone metabolism in the hypothalamus. However, seasonal rhythms persist in constant conditions in many species in the absence of a changing photoperiod signal, leading to the generation of circannual cycles. It is not known which cells, tissues, and pathways generate these remarkable long-term rhythmic processes. We show that individual PT thyrotrophs can be in one of two binary states reflecting either a long (EYA3(+)) or short (CHGA(+)) photoperiod, with the relative proportion in each state defining the phase of the circannual cycle. We also show that a morphogenic cycle driven by the PT leads to extensive re-modeling of the PT and hypothalamus over the circannual cycle. We propose that the PT may employ a recapitulated developmental pathway to drive changes in morphology of tissues and cells. Our data are consistent with the hypothesis that the circannual timer may reside within the PT thyrotroph and is encoded by a binary switch timing mechanism, which may regulate the generation of circannual neuroendocrine rhythms, leading to dynamic re-modeling of the hypothalamic interface. In summary, the PT-ventral hypothalamus now appears to be a prime structure involved in long-term rhythm generation.
Gene Expression in Mouse Thyrotrope Adenoma: Transcription Elongation Factor Stimulates Proliferation.
Thyrotrope hyperplasia and hypertrophy are common responses to primary hypothyroidism. To understand the genetic regulation of these processes, we studied gene expression changes in the pituitaries of Cga(-/-) mice, which are deficient in the common α-subunit of TSH, LH, and FSH. These mice have thyrotrope hypertrophy and hyperplasia and develop thyrotrope adenoma. We report that cell proliferation is increased, but the expression of most stem cell markers is unchanged. The α-subunit is required for secretion of the glycoprotein hormone β-subunits, and mutants exhibit elevated expression of many genes involved in the unfolded protein response, consistent with dilation and stress of the endoplasmic reticulum. Mutants have elevated expression of transcription factors that are important in thyrotrope function, such as Gata2 and Islet 1, and those that stimulate proliferation, including Nupr1, E2f1, and Etv5. We characterized the expression and function of a novel, overexpressed gene, transcription elongation factor A (SII)-like 5 (Tceal5). Stable expression of Tceal5 in a pituitary progenitor cell line is sufficient to increase cell proliferation. Thus, Tceal5 may act as a proto-oncogene. This study provides a rich resource for comparing pituitary transcriptomes and an analysis of gene expression networks.
Spatially coordinated dynamic gene transcription in living pituitary tissue.
Transcription at individual genes in single cells is often pulsatile and stochastic. A key question emerges regarding how this behaviour contributes to tissue phenotype, but it has been a challenge to quantitatively analyse this in living cells over time, as opposed to studying snap-shots of gene expression state. We have used imaging of reporter gene expression to track transcription in living pituitary tissue. We integrated live-cell imaging data with statistical modelling for quantitative real-time estimation of the timing of switching between transcriptional states across a whole tissue. Multiple levels of transcription rate were identified, indicating that gene expression is not a simple binary 'on-off' process. Immature tissue displayed shorter durations of high-expressing states than the adult. In adult pituitary tissue, direct cell contacts involving gap junctions allowed local spatial coordination of prolactin gene expression. Our findings identify how heterogeneous transcriptional dynamics of single cells may contribute to overall tissue behaviour.