No evidence for brown adipose tissue activation after creatine supplementation in adult vegetarians.

Creatine availability in adipose tissue has been shown to have profound effects on thermogenesis and energy balance in mice. However, whether dietary creatine supplementation affects brown adipose tissue (BAT) activation in humans is unclear. In the present study, we report the results of a double-blind, randomized, placebo-controlled, cross-over trial (NCT04086381) in which 14 young, healthy, vegetarian adults, who are characterized by low creatine levels, received 20 g of creatine monohydrate per day or placebo. Participants were eligible if they met the following criteria: male or female, white, aged 18-30 years, consuming a vegetarian diet (≥6 months) and body mass index 20-25 kg m-2. BAT activation after acute cold exposure was determined by calculating standard uptake values (SUVs) acquired by [18F]fluorodeoxyglucose positron emission tomography-magnetic resonance imaging. BAT volume (-31.32 (19.32) SUV (95% confidence interval (CI) -73.06, 10.42; P = 0.129)), SUVmean (-0.34 (0.29) SUV (95% CI -0.97, 0.28; P = 0.254)) and SUVmax (-2.49 (2.64) SUV (95% CI -8.20, 3.21; P = 0.362)) following acute cold exposure were similar between placebo and creatine supplementation. No side effects of creatine supplementation were reported; one participant experienced bowel complaints during placebo, which resolved without intervention. Our data show that creatine monohydrate supplementation in young, healthy, lean, vegetarian adults does not enhance BAT activation after acute cold exposure.

Facultative protein selenation regulates redox sensitivity, adipose tissue thermogenesis, and obesity.

Oxidation of cysteine thiols by physiological reactive oxygen species (ROS) initiates thermogenesis in brown and beige adipose tissues. Cellular selenocysteines, where sulfur is replaced with selenium, exhibit enhanced reactivity with ROS. Despite their critical roles in physiology, methods for broad and direct detection of proteogenic selenocysteines are limited. Here we developed a mass spectrometric method to interrogate incorporation of selenium into proteins. Unexpectedly, this approach revealed facultative incorporation of selenium as selenocysteine or selenomethionine into proteins that lack canonical encoding for selenocysteine. Selenium was selectively incorporated into regulatory sites on key metabolic proteins, including as selenocysteine-replacing cysteine at position 253 in uncoupling protein 1 (UCP1). This facultative utilization of selenium was initiated by increasing cellular levels of organic, but not inorganic, forms of selenium. Remarkably, dietary selenium supplementation elevated facultative incorporation into UCP1, elevated energy expenditure through thermogenic adipose tissue, and protected against obesity. Together, these findings reveal the existence of facultative protein selenation, which correlates with impacts on thermogenic adipocyte function and presumably other biological processes as well.

Activation of the PPAR/PGC-1alpha pathway prevents a bioenergetic deficit and effectively improves a mitochondrial myopathy phenotype.

Neuromuscular disorders with defects in the mitochondrial ATP-generating system affect a large number of children and adults worldwide, but remain without treatment. We used a mouse model of mitochondrial myopathy, caused by a cytochrome c oxidase deficiency, to evaluate the effect of induced mitochondrial biogenesis on the course of the disease. Mitochondrial biogenesis was induced either by transgenic expression of peroxisome proliferator-activated receptor gamma (PPARgamma) coactivator alpha (PGC-1alpha) in skeletal muscle or by administration of bezafibrate, a PPAR panagonist. Both strategies successfully stimulated residual respiratory capacity in muscle tissue. Mitochondrial proliferation resulted in an enhanced OXPHOS capacity per muscle mass. As a consequence, ATP levels were conserved resulting in a delayed onset of the myopathy and a markedly prolonged life span. Thus, induction of mitochondrial biogenesis through pharmacological or metabolic modulation of the PPAR/PGC-1alpha pathway promises to be an effective therapeutic approach for mitochondrial disorders.

Gene expression-based screening identifies microtubule inhibitors as inducers of PGC-1alpha and oxidative phosphorylation.

The transcriptional coactivator PGC-1alpha is a potent regulator of several metabolic pathways, including, in particular, the activation of oxidative phosphorylation and mitochondrial biogenesis. Recent evidence suggests that increasing PGC-1alpha activity may have beneficial effects in various conditions, including muscular dystrophy, diabetes, and neurodegenerative diseases. We describe here a high-throughput screen to identify small molecules that induce PGC-1alpha expression in skeletal muscle cells. A number of drug classes are identified, including glucocorticoids, microtubule inhibitors, and protein synthesis inhibitors. These drugs induce PGC-1alpha mRNA, and the expression of a number of genes known to be regulated by PGC-1alpha. No induction of these target genes is seen in PGC-1alpha -/- cells, demonstrating that the drugs act through PGC-1alpha. These data demonstrate the feasibility of high-throughput screening for inducers of PGC-1alpha. Moreover, the data identify microtubule inhibitors and protein synthesis inhibitors as modulators of PGC-1alpha and oxidative phosphorylation.

Bioenergetic analysis of peroxisome proliferator-activated receptor gamma coactivators 1alpha and 1beta (PGC-1alpha and PGC-1beta) in muscle cells.

Peroxisome proliferator-activated receptor gamma coactivator (PGC)-1alpha is a coactivator of nuclear receptors and other transcription factors that regulates several components of energy metabolism, particularly certain aspects of adaptive thermogenesis in brown fat and skeletal muscle, hepatic gluconeogenesis, and fiber type switching in skeletal muscle. PGC-1alpha has been shown to induce mitochondrial biogenesis when expressed in muscle cells, and preliminary analysis has suggested that this molecule may specifically increase the fraction of uncoupled versus coupled respiration. In this paper, we have performed detailed bioenergetic analyses of the function of PGC-1alpha and its homolog PGC-1beta in muscle cells by monitoring simultaneously oxygen consumption and membrane potential. Cells expressing PGC-1alpha or PGC-1beta display higher proton leak rates at any given membrane potential than control cells. However, cells expressing PGC-1alpha have a higher proportion of their mitochondrial respiration linked to proton leak than cells expressing PGC-1beta. Although these two proteins cause a similar increase in the expression of many mitochondrial genes, PGC-1beta preferentially induces certain genes involved in the removal of reactive oxygen species, recently recognized as activators of uncoupling proteins. Together, these data indicate that PGC-1alpha and PGC-1beta profoundly alter mitochondrial metabolism and suggest that these proteins are likely to play different physiological functions.