SUMMARY Inherited mitochondrial DNA (mtDNA) mutations cause severe human disease. In most species, mitochondria are inherited maternally through mechanisms that are poorly understood. Genes that specifically control the inheritance of mitochondria in the germline are unknown. Here, we show that the long isoform of the protein Oskar regulates the maternal inheritance of mitochondria in Drosophila melanogaster. We show that during oogenesis mitochondria accumulate at the oocyte posterior concurrent with the bulk streaming and churning of the oocyte cytoplasm. Long Oskar traps and maintains mitochondria at the posterior at the site of primordial germ cell (PGC) formation through an actin-dependent mechanism. Mutating long oskar strongly reduces the number of mtDNA molecules inherited by PGCs. Therefore, Long Oskar ensures germline transmission of mitochondria to the next generation. These results provide molecular insight into how mitochondria are passed from mother to offspring, and also how they are positioned and asymmetrically partitioned within polarized cells.

Brown adipose tissue (BAT) dissipates nutritional energy as heat via the uncoupling protein-1 (UCP1) and BAT activity correlates with leanness in human adults. Here we profile G protein-coupled receptors (GPCRs) in brown adipocytes to identify druggable regulators of BAT. Twenty-one per cent of the GPCRs link to the Gq family, and inhibition of Gq signalling enhances differentiation of human and murine brown adipocytes. In contrast, activation of Gq signalling abrogates brown adipogenesis. We further identify the endothelin/Ednra pathway as an autocrine activator of Gq signalling in brown adipocytes. Expression of a constitutively active Gq protein in mice reduces UCP1 expression in BAT, whole-body energy expenditure and the number of brown-like/beige cells in white adipose tissue (WAT). Furthermore, expression of Gq in human WAT inversely correlates with UCP1 expression. Thus, our data indicate that Gq signalling regulates brown/beige adipocytes and inhibition of Gq signalling may be a novel therapeutic approach to combat obesity.

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ObjectiveMaternal and environmental factors control the epigenetic fetal programming of the embryo, thereby defining the susceptibility for metabolic or endocrine disorders in the offspring. Pharmacological interventions required as a consequence of gestational problems, e.g. hypertension, can potentially interfere with correct fetal programming. As epigenetic alterations are usually only revealed later in life and not detected in studies focusing on early perinatal outcomes, little is known about the long-term epigenetic effects of gestational drug treatments. We sought to test the consequences of maternal α1-adrenergic antagonism during pregnancy, which can occur e.g. during hypertension treatment, for the endocrine and metabolic phenotype of the offspring.MethodsWe treated C57BL/6NCrl female mice with the α1-adrenergic antagonist prazosin during pregnancy and analyzed the male and female offspring for endocrine and metabolic abnormalities.ResultsOur data revealed that maternal α1-adrenergic blockade caused dwarfism, elevated body temperature, and insulin resistance in male offspring, accompanied by reduced IGF-1 serum concentrations as the result of reduced hepatic growth hormone receptor (Ghr) expression. We subsequently identified increased CpG DNA methylation at the transcriptional start site of the alternative Ghr promotor caused by the maternal treatment, which showed a strong inverse correlation to hepatic Ghr expression.ConclusionsOur results demonstrate that maternal α1-adrenergic blockade can constitute an epigenetic cause for dwarfism and insulin resistance. The findings are of immediate clinical relevance as combined α/β-adrenergic blockers are first-line treatment of maternal hypertension.

Stimulation of thermogenic pathways appears to be a promising approach to find new ways of tackling metabolic diseases like obesity and diabetes mellitus type 2. Thermogenic, weight reducing and insulin sensitizing effects of phosphodiesterase 5 (PDE 5) inhibitors have recently been postulated, suggesting that modulators of endogenous cGMP signaling have the therapeutic potential to treat metabolic disorders. However, most studies have been performed in vitro or in animals that were not glucose intolerant. We, thus, aimed to test the metabolic effects of the PDE 5 inhibitor sildenafil by treating diet-induced obese (DIO) mice orally for 8 days. Surprisingly, our results revealed no changes in body temperature, brown adipose tissue (BAT) thermogenesis and gene expression in BAT and inguinal white adipose tissue (iWAT), thus excluding a thermogenic or 'browning' effect of sildenafil in preexisting obesity. In contrast, sildenafil-treated DIO mice displayed changes in liver metabolism and glucose homeostasis resulting in impaired glucose tolerance (P < 0.05), demonstrating for the first time an unfavorable metabolic effect of increased hepatic cGMP signaling in obesity. As sildenafil is commonly prescribed to treat pulmonary arterial hypertension and erectile dysfunction in diabetic and/or obese patients, follow up studies are urgently required to re-evaluate the drug safety.

Introduction: Injection of 3-iodothyronamine into experimental animals profoundly affects their metabolism and body temperature. As 3-iodothyronamine is rapidly acetylated in vivo after injection, it was hypothesized that the metabolites N- or O-acetyl-3-iodothyronamines could constitute the active hormones. Methods: Adult male mice were injected once daily with one of the metabolites (5 mg/kg body weight intraperitoneally dissolved in 60% DMSO in PBS) or solvent. Metabolism was monitored by indirect calorimetry, body temperature by infrared thermography, and body composition by nuclear magnetic resonance analysis. Signaling activities in brown fat or liver were assessed by studying target gene transcription by qPCR including uncoupling protein 1 or deiodinase type 1 or 2, and Western blot. Results: The markers of metabolism, body composition, or temperature tested were similar in the mice injected with solvent and those injected with one of the acetylated 3-iodothyronamines. Conclusions: In our experimental setup, N- and O-acetyl-3-iodothyronamine do not constitute compounds contributing to the metabolic or temperature effects described for 3-iodothyronamine. The acetylation of 3-iodothyronamine observed in vivo may thus rather serve degradation and elimination purposes.

Highlights d Ambient temperature during pregnancy programs male offspring's metabolism d The level of maternal BAT thermogenesis determines male offspring's lean mass d Female offspring are not affected by altered maternal BAT thermogenesis d Fetal programming effects by maternal BAT thermogenesis are reversed by exercise