Chronic serotonin reuptake inhibition uncouples brown fat mitochondria and induces beiging/browning process of white fat in overfed rats

Overweight during development dysregulates cellular metabolism and critical genes that control food intake in the prefrontal cortex

BACKGROUNDS AND AIMS

Childhood obesity is increasing substantially across the world. The World Obesity Federation (WOF) and World Health Organization (WHO) predicted that in 2030 > 1 billion people will be obese, and by 2035 over 4 billion will reach obesity worldwide. According to WHO, the world soon cannot afford the economic cost of obesity, and we need to act to stop obesity acceleration now. Data in the literature supports that the first 1000 days of life are essential in preventing obesity and related adversities. Therefore, using basic research, the present a study that focuses on the immediate effect of overnutrition and serotonin modulation during the lactation period.

METHODS

Using a neonatal overfeeding model, male Wistar rats were divided into four groups based on nutrition or serotonin modulation by pharmacological treatment up to 22 days of life. Cellular and mitochondrial function markers, oxidative stress biomarkers and mRNA levels of hedonic and homeostatic genes were evaluated.

RESULTS

Our data showed that overfeeding during lactation decrease NAD/NADH ratio, citrate synthase activity, and increase ROS production. Lipid and protein oxidation were increased in overfed animals, with a decrease in antioxidant defenses, we also observe a differential expression of mRNA levels of homeostatic and hedonic genes. On the contrary, serotonin modulation with selective serotonin reuptake inhibitors treatment reduces harmful effects caused by overnutrition.

CONCLUSION

Early effects of overnutrition significantly affect the prefrontal cortex at molecular and cellular level, which could mediate obesity-related neurodegenerative dysfunction.

Cooling down with Entresto. Can sacubitril/valsartan combination enhance browning more than coldness?

BACKGROUND

It is a growing importance to induce a new treatment approach to encourage weight loss but also to improve maintenance of lost weight. It has been shown that promotion of brown adipose tissue (BAT) function or acquisition of BAT characteristics in white adipose tissue (terms referred as "browning") can be protective against obesity.

MAIN TEXT

Amongst numerous established environmental influences on BAT activity, cold exposure is the best interested technique due to its not only effects on of BAT depots in proliferation process but also de novo differentiation of precursor cells via β-adrenergic receptor activation. A novel combination drug, sacubitril/valsartan, has been shown to be more efficient in reducing cardiovascular events and heart failure readmission compared to conventional therapy. Also, this combination of drugs increases the postprandial lipid oxidation contributing to energy expenditure, promotes lipolysis in adipocytes and reduces body weight. To date, there is no research examining potential of combined sacubitril/valsartan use to promote browning or mechanisms in the basis of this thermogenic process.

CONCLUSION

Due to the pronounced effects of cold and sacubitril/valsartan treatment on function and metabolism of BAT, the primary goal of further research should focused on investigation of the synergistic effects of the sacubitril/valsartan treatment at low temperature environmental conditions.

Overfeeding during development induces temporally-dependent changes in areas controlling food intake in the brains of male Wistar rats

AIMS

We sought to evaluate the effects of overfeeding during lactation on the feeding behavior and expression of specific regulatory genes in brain areas associated with food intake in 22- and 60-day old male rats.

METHODS

We evaluated body weight, food intake of standard and palatable diet, and mRNA expression of dopamine receptor D1 (DDR1), dopamine receptor (DDR2), melanocortin 4 receptor (MC4R), the μ-opioid receptor (MOR), neuropeptide Y (NPY), agouti-related protein (AGRP), proopiomelanocortin (POMC), cocaine-and amphetamine-regulated transcript (CART), serotonin (5-hydroxytryptamine; 5-HT) transporter (SERT), 5-hydroxytryptamine receptor 1B (5-HT1B), 5-hydroxytryptamine receptor 2C receptor (5-HT2C), Clock (CLOK), cryptochrome protein 1 (Cry1) and period circadian protein homolog 2 (Per2) in the striatum, hypothalamus and brainstem of male rats at post-natal days (PND) 22 and 60.

KEY FINDINGS

Overfeeding resulted in significantly increased body weight through PND60, and a 2-fold increase in palatable food intake at PND22, but not at PND60. We observed significant increases in DDR1, DDR2, and MC4R gene expression in the striatum and brainstem and POMC/CART in the hypothalamus of the OF group at PND22 that were reversed by PND60. Hypothalamic levels of 5-HT1B, 5-HT2C and NPY/AGRP on the other hand were decreased at PND22 and increased at PND60 in OF animals. Clock genes were unaffected by OF at PND22, but were significantly elevated at PND60.

SIGNIFICANCE

Overfeeding during early development of the rat brain results in obesity and altered feeding behavior in early adulthood. The altered behavior might be the consequence of the changes in food intake and reward gene expression.

Cold-Pressed Nigella Sativa Oil Standardized to 3% Thymoquinone Potentiates Omega-3 Protection against Obesity-Induced Oxidative Stress, Inflammation, and Markers of Insulin Resistance Accompanied with Conversion of White to Beige Fat in Mice

Excessive lipid accumulation in white adipose tissue (WAT) results in adipocyte hypertrophy and chronic low-grade inflammation, which is the major cause of obesity-associated insulin resistance and consequent metabolic disease. The development of beige adipocytes in WAT (browning of WAT) increases energy expenditure and has been considered as a novel strategy to counteract obesity. Thymoquinone (TQ) is the main bioactive quinone derived from the plant Nigella Sativa and has antioxidative and anti-inflammatory capacities. Fish oil omega 3 (ω3) enhances both insulin sensitivity and glucose homeostasis in obesity, but the involved mechanisms remain unclear. The aim of this study is to explore the effects of TQ and ω3 PUFAs (polyunsaturated fatty acids) on obesity-associated inflammation, markers of insulin resistance, and the metabolic effects of adipose tissue browning. 3T3-L1 cells were cultured to investigate the effects of TQ and ω3 on the browning of WAT. C57BL/6J mice were fed a high-fat diet (HFD), supplemented with 0.75% TQ, and 2% ω3 in combination for eight weeks. In 3T3-L1 cells, TQ and ω3 reduced lipid droplet size and increased hallmarks of beige adipocytes such as uncoupling protein-1 (UCP1), PR domain containing 16 (PRDM16), fibroblast growth factor 21 (FGF21), Sirtuin 1 (Sirt1), Mitofusion 2 (Mfn2), and heme oxygenase 1 (HO-1) protein expression, as well as increased the phosphorylation of Protein Kinase B (AKT) and insulin receptors. In the adipose tissue of HFD mice, TQ and ω3 treatment attenuated levels of inflammatory adipokines, Nephroblastoma Overexpressed (NOV/CCN3) and Twist related protein 2 (TWIST2), and diminished adipocyte hypoxia by decreasing HIF1α expression and hallmarks of beige adipocytes such as UCP1, PRDM16, FGF21, and mitochondrial biogenesis markers Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), Sirt1, and Mfn2. Increased 5′ adenosine monophosphate-activated protein kinase (AMPK) and acetyl-CoA carboxylase (ACC) phosphorylation and HO-1 expression were observed in adipose with TQ and ω3 treatment, which led to increased pAKT and pIRS1 Ser³⁰⁷ expression. In addition to the adipose, TQ and ω3 also increased inflammation and markers of insulin sensitivity in the liver, as demonstrated by increased phosphorylated insulin receptor (pIR tyr⁹⁷²), insulin receptor beta (IRβ), UCP1, and pIRS1 Ser³⁰⁷ and reduced NOV/CCN3 expression. Our data demonstrate the enhanced browning of WAT from TQ treatment in combination with ω3, which may play an important role in decreasing obesity-associated insulin resistance and in reducing the chronic inflammatory state of obesity.

Fluoxetine administration in juvenile overfed rats improves hypothalamic mitochondrial respiration and REDOX status and induces mitochondrial biogenesis transcriptional expression

Nutritional imbalance in early life may disrupt the hypothalamic control of energy homeostasis and increase the risk of metabolic disease. The hypothalamic serotonin (5-hydroxytryptamine; 5-HT) system based in the hypothalamus plays an important role in the homeostatic control of energy balance, however the mechanisms underlying the regulation of energy metabolism by 5-HT remain poorly described. Several crucial mitochondrial functions are altered by mitochondrial stress. Adaptations to this stress include changes in mitochondrial multiplication (i.e, mitochondrial biogenesis). Due to the scarcity of evidence regarding the effects of serotonin reuptake inhibitors (SSRI) such as fluoxetine (FLX) on mitochondrial function, we sought to investigate the potential contribution of FLX on changes in mitochondrial function and biogenesis occurring in overfed rats. Using a neonatal overfeeding model, male Wistar rats were divided into 4 groups between 39 and 59 days of age based on nutrition and FLX administration: normofed + vehicle (NV), normofed + FLX (NF), overfed + vehicle (OV) and overfed + FLX (OF). We found that neonatal overfeeding impaired mitochondrial respiration and increased oxidative stress biomarkers in the hypothalamus. FLX administration in overfed rats reestablished mitochondrial oxygen consumption, increased mitochondrial uncoupling protein 2 (Ucp2) expression, reduced total reactive species (RS) production and oxidative stress biomarkers, and up-regulated mitochondrial biogenesis-related genes. Taken together our results suggest that FLX administration in overfed rats improves mitochondrial respiratory chain activity and oxidative balance and increases the transcription of genes employed in mitochondrial biogenesis favoring mitochondrial energy efficiency in response to early nutritional imbalance.