Exercise-Induced Adaptations to Adipose Tissue Thermogenesis

Reframing Diabetes Prevention: From Body Shaming to Metabolic Reprogramming

This review integrates new developments in psychology with updated physiological insight on the complex relationships among chronic psychological stress (arising from weight stigmatization and body shaming), food composition, physical activity and metabolic health for the example of diabetes. We address how visual measures of health, such as body mass index (BMI) and waist-to-hip ratio, do not adequately capture metabolic health and can instead contribute to weight stigmatization, chronic stress, and system-wide impairment of metabolic health. We also emphasize the importance of food composition over calorie counting. We summarize how chronic stress interacts with nutritional deficiencies and physical inactivity to disrupt the stress response, immune response, gut microbiome, and function of fat depots. We specifically address how interactions among lifestyle factors and the gut microbiome regulate whether fat stored around the waist has a negative or positive effect on metabolic health. We aim to provide a resource and updated framework for diabetes prevention and health promotion by (i) highlighting metabolic imbalances triggered by lifestyle changes during the transition to industrialized society and (ii) detailing the potential to support metabolic health through access to modest, but comprehensive lifestyle adjustments.

Effects of Fish Oil with Heat Treatment on Obesity, Inflammation, and Gut Microbiota in Ovariectomized Mice

Background/Objectives: Menopause induces substantial metabolic changes, including a reduction in metabolic rate and an elevated risk of developing metabolic diseases. Fish oil (FO) supplementation has been shown to ameliorate menopause-associated metabolic risks. Hyperthermia treatment (HT) has recently gained attention for its potential to improve metabolic and immune health. However, it remains to be determined whether HT can confer metabolic benefits comparable to those of FO supplementation or enhance the metabolic benefits of FO supplementation. This study aims to delineate the distinctive and collaborative effects of HT and FO supplementation in mitigating menopause-associated metabolic dysfunction. Methods: Female C57BL/6 ovariectomized (OVX) mice were randomly assigned to four groups (n = 12/group) to evaluate the individual and combined effects of FO supplementation (5% w/w) and HT treatment. For HT, whole-body heat exposure was conducted at 40-41 °C for 30 min, 5 days per week. After 12 weeks, animals were used to evaluate the changes in glucose and lipid metabolism, obesity outcome, and inflammatory markers. The gut microbiome analysis was conducted from cecal content by 16S rRNA sequencing. Acute inflammation was induced by lipopolysaccharide (LPS) injection to evaluate inflammatory responses. Results: HT alone distinctively reduced weight gain, lowered core body temperature, and attenuated insulin resistance comparable to FO supplement in OVX mice. The collaborative effect of FO and HT was not evident in metabolic parameters but more prominent in attenuating proinflammatory responses and microbiota modulation. Conclusions: Our findings suggest that the combined treatment of FO supplementation and HT may serve as an effective strategy to mitigate menopause-associated immune susceptibility and metabolic dysfunction. These benefits are likely mediated, at least in part, through the reduction in inflammation and modulation of the gut microbiota.

Exercise as a Therapeutic Strategy for Obesity: Central and Peripheral Mechanisms

Obesity is a complex, multifactorial condition involving excessive fat accumulation due to an imbalance between energy intake and expenditure, with its global prevalence steadily rising. This condition significantly increases the risk of chronic diseases, including sarcopenia, type 2 diabetes, and cardiovascular diseases, highlighting the need for effective interventions. Exercise has emerged as a potent non-pharmacological approach to combat obesity, targeting both central and peripheral mechanisms that regulate metabolism, energy expenditure, and neurological functions. In the central nervous system, exercise influences appetite, mood, and cognitive functions by modulating the reward system and regulating appetite-controlling hormones to manage energy intake. Concurrently, exercise promotes thermogenesis in adipose tissue and regulates endocrine path-ways and key metabolic organs, such as skeletal muscle and the liver, to enhance fat oxidation and support energy balance. Despite advances in understanding exercise's role in obesity, the precise interaction between the neurobiological and peripheral metabolic pathways remains underexplored, particularly in public health strategies. A better understanding of these interactions could inform more comprehensive obesity management approaches by addressing both central nervous system influences on behavior and peripheral metabolic regulation. This review synthesizes recent insights into these roles, highlighting potential therapeutic strategies targeting both systems for more effective obesity interventions.

Exploring the Impact of Resistance Training at Moderate Altitude on Metabolic Cytokines in Humans: Implications for Adipose Tissue Dynamics

Hypobaric hypoxia (HH) limits oxygen supply to tissues and increases metabolic demands, especially during exercise. We studied the influence of HH exposure on the subcutaneous adipose tissue (SAT) thickness and circulating metabolic-related cytokines levels after a resistance training (RT) program. Twenty trained men participated in a traditional hypertrophy RT for 8 weeks (three sessions/week) under intermittent terrestrial HH (2320 m) or normoxia (N, 690 m) conditions. Before, at week 6, and after the RT, SAT, and vastus lateralis (VL) muscle thickness were measured by ultrasound. Blood samples were taken to analyse serum cytokines (IL-6, IL-15, irisin, and myostatin) by multiplex immunoassay. Our findings revealed a moderate reduction in IL-6 and irisin in HH following the RT (ES < -0.64; p < 0.05). Additionally, RT in HH promoted serum IL-15 release (ES = 0.890; p = 0.062), which exhibited a trivial inverse association with the reductions observed on SAT (-17.69%; p < 0.001) compared with N. RT in HH explained ~50% of SAT variance (p < 0.001). These results highlight the benefit of stressor factors linked to RT in HH on SAT through the modulation of serum metabolic cytokine profiles, suggesting a potential effect on overall body composition.

Exercise as a tool to mitigate metabolic disease

Metabolic diseases, notably obesity and type 2 diabetes (T2D), have reached alarming proportions and constitute a significant global health challenge, emphasizing the urgent need for effective preventive and therapeutic strategies. In contrast, exercise training emerges as a potent intervention, exerting numerous positive effects on metabolic health through adaptations to the metabolic tissues. Here, we reviewed the major features of our current understanding with respect to the intricate interplay between metabolic diseases and key metabolic tissues, including adipose tissue, skeletal muscle, and liver, describing some of the main underlying mechanisms driving pathogenesis, as well as the role of exercise to combat and treat obesity and metabolic disease.

Molecular adaptations in response to exercise training are associated with tissue-specific transcriptomic and epigenomic signatures

Regular exercise has many physical and brain health benefits, yet the molecular mechanisms mediating exercise effects across tissues remain poorly understood. Here we analyzed 400 high-quality DNA methylation, ATAC-seq, and RNA-seq datasets from eight tissues from control and endurance exercise-trained (EET) rats. Integration of baseline datasets mapped the gene location dependence of epigenetic control features and identified differing regulatory landscapes in each tissue. The transcriptional responses to 8 weeks of EET showed little overlap across tissues and predominantly comprised tissue-type enriched genes. We identified sex differences in the transcriptomic and epigenomic changes induced by EET. However, the sex-biased gene responses were linked to shared signaling pathways. We found that many G protein-coupled receptor-encoding genes are regulated by EET, suggesting a role for these receptors in mediating the molecular adaptations to training across tissues. Our findings provide new insights into the mechanisms underlying EET-induced health benefits across organs.

TRP channels associated with macrophages as targets for the treatment of obese asthma

Globally, obesity and asthma pose significant health challenges, with obesity being a key factor influencing asthma. Despite this, effective treatments for obese asthma, a distinct phenotype, remain elusive. Since the discovery of transient receptor potential (TRP) channels in 1969, their value as therapeutic targets for various diseases has been acknowledged. TRP channels, present in adipose tissue cells, influence fat cell heat production and the secretion of adipokines and cytokines, which are closely associated with asthma and obesity. This paper aims to investigate the mechanisms by which obesity exacerbates asthma-related inflammation and suggests that targeting TRP channels in adipose tissue could potentially suppress obese asthma and offer novel insights into its treatment.

Effects of aerobic, resistance, and high-intensity interval training on thermogenic gene expression in white adipose tissue in high fat diet induced obese mice

OBJECTIVE

Global prevalence of obesity has continued to rise and poses public health concerns. Current anti-obesity medications are mainly focused on suppressing appetite. Thermogenic fat cells that increase energy expenditure may be a promising alternative target to combat obesity. Our study aims to investigate the effects of aerobic, resistance, and high-intensity interval training on thermogenic gene expression in white adipose tissue in high fat diet induced obese mice.

METHODS

Fifty 6-week-old male C57BL/6 mice were initially divided into control group and high fat diet group for obesity induction. After 8 weeks of obesity induction, obese mice were subdivided into sedentary, aerobic exercise, resistance exercise, and high intensity interval training groups. Trained obese mice were submitted to 8 weeks of exercise.

RESULTS

Our results showed that all three exercises significantly decreased body weight, and improved metabolic profiles including glucose tolerance, total cholesterol, and low-density lipoprotein cholesterol. Moreover, aerobic exercise training increases serum irisin levels and thermogenic gene expressions such as Prdm16, Cidea, and Pgc-1α in epididymal white adipose tissue of obese mice.

CONCLUSION

Our findings suggest that when it comes to the adaption of thermogenic fat cells, the modality of exercise should be taken into consideration. Aerobic exercise may induce a modest increase in the expression levels of certain thermogenic genes in epididymal white adipose tissue.

Regulatory effects and mechanisms of exercise on activation of brown adipose tissue (BAT) and browning of white adipose tissue (WAT)

Exercise is a universally acknowledged and healthy way to reducing body weight. However, the roles and mechanisms of exercise on metabolism of adipose tissue remain largely unclear. Adipose tissues include white adipose tissue (WAT), brown adipose tissue (BAT) and beige adipose tissue (BeAT). The main function of WAT is to store energy, while the BAT and BeAT can generate heat and consume energy. Therefore, promotion of BAT activation and WAT browning contributes to body weight loss. To date, many studies have suggested that exercise exerts the potential regulatory effects on BAT activation and WAT browning. In the present review, we compile the evidence for the regulatory effects of exercise on BAT activation and WAT browning and summarize the possible mechanisms whereby exercise modulates BAT activation and WAT browning, including activating sympathetic nervous system (SNS) and promoting the secretion of exerkines, with special focus on exerkines. These data might provide reference for prevention or treatment of obesity and the related metabolic disease through exercise.

Phosphorylated YBX2 is stabilized to promote glycolysis in brown adipocytes

Y-box binding protein 2 (YBX2) is an essential modulator of brown adipose tissue activation, yet the regulation on its own expression and the involved mechanism remains largely unknown. Herein, we report the YBX2 protein level, but not mRNA level, is induced in response to acute β-adrenergic signaling. In this context, YBX2 is a dual substrate for both AMPK and Akt2. The phosphorylation at Thr115 by AMPK or at Ser137 by Akt2 facilitates YBX2 accumulation in brown adipocytes by decreasing ubiquitination-mediated degradation. Beyond stabilizing PGC1α mRNA, increased YBX2 upon thermogenic activation assists the expression of glycolytic enzymes, promotes glucose utilization and lactate production. Mechanistically, YBX2 modulates translation of glycolytic genes via direct binding to 5'-UTRs of these genes. Together these findings suggest YBX2 is responsive to thermogenic stimuli by phosphorylation modification, and stabilized YBX2 helps to boost glycolysis and thermogenesis in brown adipocytes.

Master of disguise: deconvoluting adipose tissue heterogeneity and its impact on metabolic health

Adipose tissue in its different forms: white, brown, and beige, while essential in day-to-day bodily functions, leads to several disorders when present in overabundance, including obesity and type-2 diabetes. Adipose tissue function/dysfunction is largely mediated by the diversity of its cell composition, within adipocytes and cells in its stromal fraction. Owing to its heterogeneous nature, recent studies have focused on intercalating the effects of cellular diversity with adipose tissue function, particularly by employing sequencing technologies. In this review, we highlight the recent advances in utilizing single-cell and single-nuclei RNA sequencing technologies to discover novel adipose tissue cell types or subtypes, and to determine their role in mediating tissue, as well as whole-body metabolism and function.

Brown adipose tissue and aging: A potential role for exercise

Aging is one of the primary risk factors for the development of type 2 diabetes and cardiovascular disease, and regular physical activity can help to delay, prevent, or manage the onset and development of many chronic diseases present in older adults. Brown adipose tissue (BAT) is thermogenic tissue that protects against age-related disease, but BAT activity decreases with age. In this review, we discuss how aging contributes to impaired BAT function by inducing a 'whitening' of the BAT and altering beta 3 adrenergic receptor (β3AR) signaling, uncoupling protein 1 (UCP1) gene expression, and mitochondria respiration, and potential mechanisms for exercise to counteract the effects of aging on BAT.

Dynamic of irisin secretion change after moderate-intensity chronic physical exercise on obese female

OBJECTIVES

Exercise is one of the beneficial mediators for the regulation and prevention of obesity through the role of irisin, so it potentially enhances metabolism health. This study aims to investigate the dynamic of irisin secrecy change after chronic exercise in obese females.

METHODS

Thirty-one female adolescents aged 20-22 years enrolled in the study and were given interventions aerobic, resistance, and a combination of aerobic and resistance training. The exercises were performed at moderate-intensity, for 35-40 min per session, and three times a week for four weeks. The measurement of irisin level, IGF-1 level, and bio-anthropometry was carried out before and after the four weeks of exercise. The bio-anthropometry measurement was carried out using seca mBCA 514, while the measurement of insulin-like growth factor 1 (IGF-1) and irisin was completed using an enzyme-linked immunosorbent assay (ELISA). The obtained data were analyzed using a one-way ANOVA test with 5 % significance.

RESULTS

Our results indicated higher dynamic of irisin and IGF-1 increases in the group with a combination of aerobic and resistance training exercises than the other two groups with a different exercise. Further, we also observed different dynamics of irisin and IGF-1 level increase (p<0.05). Besides, the irisin was also correlated with the IGF-1 and bio-anthropometric parameters (p<0.05).

CONCLUSIONS

The combination of aerobic and resistance training exercises is considered as the alternative for enhancing the dynamic of irisin and IGF-1 increase. Thus, it can be used to prevent and regulate obesity.

Differential remodeling of subcutaneous white and interscapular brown adipose tissue by long-term exercise training in aged obese female mice

Obesity exacerbates aging-induced adipose tissue dysfunction. This study aimed to investigate the effects of long-term exercise on inguinal white adipose tissue (iWAT) and interscapular brown adipose tissue (iBAT) of aged obese mice. Two-month-old female mice received a high-fat diet for 4 months. Then, six-month-old diet-induced obese animals were allocated to sedentarism (DIO) or to a long-term treadmill training (DIOEX) up to 18 months of age. In exercised mice, iWAT depot revealed more adaptability, with an increase in the expression of fatty acid oxidation genes (Cpt1a, Acox1), and an amelioration of the inflammatory status, with a favorable modulation of pro/antiinflammatory genes and lower macrophage infiltration. Additionally, iWAT of trained animals showed an increment in the expression of mitochondrial biogenesis (Pgc1a, Tfam, Nrf1), thermogenesis (Ucp1), and beige adipocytes genes (Cd137, Tbx1). In contrast, iBAT of aged obese mice was less responsive to exercise. Indeed, although an increase in functional brown adipocytes genes and proteins (Pgc1a, Prdm16 and UCP1) was observed, few changes were found on inflammation-related and fatty acid metabolism genes. The remodeling of iWAT and iBAT depots occurred along with an improvement in the HOMA index for insulin resistance and in glucose tolerance. In conclusion, long-term exercise effectively prevented the loss of iWAT and iBAT thermogenic properties during aging and obesity. In iWAT, the long-term exercise program also reduced the inflammatory status and stimulated a fat-oxidative gene profile. These exercise-induced adipose tissue adaptations could contribute to the beneficial effects on glucose homeostasis in aged obese mice.

Cellular and Molecular Regulation of Exercise-A Neuronal Perspective

The beneficial effects of exercise on the proper functioning of the body have been firmly established. Multi-systemic metabolic regulation of exercise is the consequence of multitudinous changes that occur at the cellular level. The exercise responsome comprises all molecular entities including exerkines, miRNA species, growth factors, signaling proteins that are elevated and activated by physical exercise. Exerkines are secretory molecules released by organs such as skeletal muscle, adipose tissue, liver, and gut as a function of acute/chronic exercise. Exerkines such as FNDC5/irisin, Cathepsin B, Adiponectin, and IL-6 circulate through the bloodstream, cross the blood-brain barrier, and modulate the expression of important signaling molecules such as AMPK, SIRT1, PGC1α, BDNF, IGF-1, and VEGF which further contribute to improved energy metabolism, glucose homeostasis, insulin sensitivity, neurogenesis, synaptic plasticity, and overall well-being of the body and brain. These molecules are also responsible for neuroprotective adaptations that exercise confers on the brain and potentially ameliorate neurodegeneration. This review aims to detail important cellular and molecular species that directly or indirectly mediate exercise-induced benefits in the body, with an emphasis on the central nervous system.

Swimming in cold water upregulates genes involved in thermogenesis and the browning of white adipose tissues

The purpose of this study was to investigate whether there is an interacting effect of six weeks of swimming in cold water on the gene expression of browning markers in adipose tissue in rodents. Twenty male Wistar rats were randomly divided into four groups: Control (C, 25 °C), Cold Exposure (CE, 4 °C), Swimming in tepid Water (STW, 30 °C), and Swimming in Cold Water (SCW, 15 °C). The swimming included 2-3 min intervals, 1 min rest, until exhaustion, three days a week for six weeks, with 3 to 6% of bodyweight overload. Rats from CE were exposed to cold for 2 h per day, five days per week. After the experimental protocol, interscapular brown (BAT) and inguinal subcutaneous white (WAT) fat tissues were excised, weighed, and processed for beiging and mitochondrial biogenesis markers gene expression. The experimental protocols resulted in an apparent increase in the number of brown adipocytes (per mm²) in the adipose deposits compared to the C group; substantial changes were observed in the SCW group. Compared to other groups, cold exposure alone increased significantly serum norepinephrine, and also β₂-adrenergic receptor expression was upregulated in the adipocytes compared to the C group. The STW group increased the expression of peroxisome proliferator-activated receptor-γ (PPAR-γ) coactivator-1 alpha (PGC-1α), β₂-adrenergic receptor, and CCAAT/enhancer-binding proteins-α(c/EBP-α) in WAT in comparison with the C group(p < 0.05). In both adipocytes, the SCW intervention significantly upregulated the expression of PGC-1α, PPAR-γ, and c/EBP-α genes in comparison with the C and CE groups. In addition, the expression of TFAM and UCP1 was upregulated substantially in the SCW group compared to other groups. Our data demonstrate that swim training and cold exposure present additive effects in the expression of genes involved in the beiging process and mitochondrial biogenesis markers in BAT and WAT. In addition, it seems that the upregulation of these genes is related to the activation of β₂-adrenergic receptors.

Thermogenic adipose tissue in energy regulation and metabolic health

The ability to generate thermogenic fat could be a targeted therapy to thwart obesity and improve metabolic health. Brown and beige adipocytes are two types of thermogenic fat cells that regulate energy balance. Both adipocytes share common morphological, biochemical, and thermogenic properties. Yet, recent evidence suggests unique features exist between brown and beige adipocytes, such as their cellular origin and thermogenic regulatory processes. Beige adipocytes also appear highly plastic, responding to environmental stimuli and interconverting between beige and white adipocyte states. Additionally, beige adipocytes appear to be metabolically heterogenic and have substrate specificity. Nevertheless, obese and aged individuals cannot develop beige adipocytes in response to thermogenic fat-inducers, creating a key clinical hurdle to their therapeutic promise. Thus, elucidating the underlying developmental, molecular, and functional mechanisms that govern thermogenic fat cells will improve our understanding of systemic energy regulation and strive for new targeted therapies to generate thermogenic fat. This review will examine the recent advances in thermogenic fat biogenesis, molecular regulation, and the potential mechanisms for their failure.

Effects of weight-bearing vs. non-weight-bearing endurance exercise on reducing body fat and inflammatory markers in obese females

OBJECTIVES

Endurance exercise is an effective strategy for maintaining an anti-inflammatory environment and weight management. However, the effect of this type of exercise on decreasing body fat and TNF-α levels and increasing adiponectin levels is controversial. The aims of this study was to prove the effects of weight-bearing vs. non-weight-bearing endurance exercise on reducing body fat and inflammatory markers in obese females.

METHODS

24 obese adolescents were recruited from female students from the State University of Malang. The interventions given in this study were weight-bearing endurance exercise (WBEE), and non-weight-bearing endurance exercise (NWBEE). Serum TNF-α levels and serum adiponectin levels were evaluated using enzyme-linked immunosorbent assay (ELISA). Statistical analysis techniques use paired sample T-test with a significant level of 5%.

RESULTS

Results of the statistical analysis show that the average body fat (PBF, FM, FFM) and TNF-α levels before endurance exercise vs. after endurance exercise in both types of exercise experienced a significant decrease (p≤0.05), while average adiponectin levels in both types of exercise experienced a significant increase before endurance exercise vs. after endurance exercise (p≤0.001).

CONCLUSIONS

In general, it can be concluded that weight-bearing and non-weight-bearing endurance exercise with moderate-intensity for 40 min/exercise session reduce body fat and TNF-α levels and increase adiponectin levels as a marker of inflammation in obese female.

Time of day determines postexercise metabolism in mouse adipose tissue

The circadian clock is a cell-autonomous transcription-translation feedback mechanism that anticipates and adapts physiology and behavior to different phases of the day. A variety of factors including hormones, temperature, food-intake, and exercise can act on tissue-specific peripheral clocks to alter the expression of genes that influence metabolism, all in a time-of-day dependent manner. The aim of this study was to elucidate the effects of exercise timing on adipose tissue metabolism. We performed RNA sequencing on inguinal adipose tissue of mice immediately following maximal exercise or sham treatment at the early rest or early active phase. Only during the early active phase did exercise elicit an immediate increase in serum nonesterified fatty acids. Furthermore, early active phase exercise increased expression of markers of thermogenesis and mitochondrial proliferation in inguinal adipose tissue. In vitro, synchronized 3T3-L1 adipocytes showed a timing-dependent difference in Adrb2 expression, as well as a greater lipolytic activity. Thus, the response of adipose tissue to exercise is time-of-day sensitive and may be partly driven by the circadian clock. To determine the influence of feeding state on the time-of-day response to exercise, we replicated the experiment in 10-h-fasted early rest phase mice to mimic the early active phase metabolic status. A 10-h fast led to a similar lipolytic response as observed after active phase exercise but did not replicate the transcriptomic response, suggesting that the observed changes in gene expression are not driven by feeding status. In conclusion, acute exercise elicits timing-specific effects on adipose tissue to maintain metabolic homeostasis.

Exercise-induced intertissue communication: adipose tissue and the heart

Exercise leads to numerous beneficial whole-body effects and can protect against the development of obesity, cardiometabolic, and neurodegenerative diseases. Recent studies have highlighted the importance of inter-organ crosstalk with a focus on secretory factors that mediate communication among organs, including adipose tissue and the heart. Studies investigating the effects of exercise on brown adipose tissue (BAT) and white adipose tissue (WAT) demonstrated that adipokines are released in response to exercise and act on the heart to decrease inflammation, alter gene expression, increase angiogenesis, and improve cardiac function. This review discusses the exercise-induced adaptations to BAT and WAT and how these adaptations affect heart health and function, while highlighting the importance of tissue crosstalk.

Neuroplasticity to autophagy cross-talk in a therapeutic effect of physical exercises and irisin in ADHD

Adaptive neuroplasticity is a pivotal mechanism for healthy brain development and maintenance, as well as its restoration in disease- and age-associated decline. Management of mental disorders such as attention deficit hyperactivity disorder (ADHD) needs interventions stimulating adaptive neuroplasticity, beyond conventional psychopharmacological treatments. Physical exercises are proposed for the management of ADHD, and also depression and aging because of evoked brain neuroplasticity. Recent progress in understanding the mechanisms of muscle-brain cross-talk pinpoints the role of the myokine irisin in the mediation of pro-cognitive and antidepressant activity of physical exercises. In this review, we discuss how irisin, which is released in the periphery as well as derived from brain cells, may interact with the mechanisms of cellular autophagy to provide protein recycling and regulation of brain-derived neurotrophic factor (BDNF) signaling via glia-mediated control of BDNF maturation, and, therefore, support neuroplasticity. We propose that the neuroplasticity associated with physical exercises is mediated in part by irisin-triggered autophagy. Since the recent findings give objectives to consider autophagy-stimulating intervention as a prerequisite for successful therapy of psychiatric disorders, irisin appears as a prototypic molecule that can activate autophagy with therapeutic goals.

Thermogenic Brown Fat in Humans: Implications in Energy Homeostasis, Obesity and Metabolic Disorders

In mammals including humans, there are two types of adipose tissue, white and brown adipose tissues (BATs). White adipose tissue is the primary site of energy storage, while BAT is a specialized tissue for non-shivering thermogenesis to dissipate energy as heat. Although BAT research has long been limited mostly in small rodents, the rediscovery of metabolically active BAT in adult humans has dramatically promoted the translational studies on BAT in health and diseases. It is now established that BAT, through its thermogenic and energy dissipating activities, plays a role in the regulation of body temperature, whole-body energy expenditure, and body fatness. Moreover, increasing evidence has demonstrated that BAT secretes various paracrine and endocrine factors, which influence other peripheral tissues and control systemic metabolic homeostasis, suggesting BAT as a metabolic regulator, other than for thermogenesis. In fact, clinical studies have revealed an association of BAT not only with metabolic disorders such as insulin resistance, diabetes, dyslipidemia, and fatty liver, but also with cardiovascular diseases including hypertension and atherosclerosis. Thus, BAT is an intriguing tissue combating obesity and related metabolic diseases. In this review, we summarize current knowledge on human BAT, focusing its patho-physiological roles in energy homeostasis, obesity and related metabolic disorders. The effects of aging and sex on BAT are also discussed.

The mitochondrial multi-omic response to exercise training across tissues

Mitochondria are adaptable organelles with diverse cellular functions critical to whole-body metabolic homeostasis. While chronic endurance exercise training is known to alter mitochondrial activity, these adaptations have not yet been systematically characterized. Here, the Molecular Transducers of Physical Activity Consortium (MoTrPAC) mapped the longitudinal, multi-omic changes in mitochondrial analytes across 19 tissues in male and female rats endurance trained for 1, 2, 4 or 8 weeks. Training elicited substantial changes in the adrenal gland, brown adipose, colon, heart and skeletal muscle, while we detected mild responses in the brain, lung, small intestine and testes. The colon response was characterized by non-linear dynamics that resulted in upregulation of mitochondrial function that was more prominent in females. Brown adipose and adrenal tissues were characterized by substantial downregulation of mitochondrial pathways. Training induced a previously unrecognized robust upregulation of mitochondrial protein abundance and acetylation in the liver, and a concomitant shift in lipid metabolism. The striated muscles demonstrated a highly coordinated response to increase oxidative capacity, with the majority of changes occurring in protein abundance and post-translational modifications. We identified exercise upregulated networks that are downregulated in human type 2 diabetes and liver cirrhosis. In both cases HSD17B10, a central dehydrogenase in multiple metabolic pathways and mitochondrial tRNA maturation, was the main hub. In summary, we provide a multi-omic, cross-tissue atlas of the mitochondrial response to training and identify candidates for prevention of disease-associated mitochondrial dysfunction.

Circulating thrifty microRNA is related to insulin sensitivity, adiposity, and energy metabolism in adults with overweight and obesity: the POUNDS Lost trial

BACKGROUND

MicroRNA 128-1 (miR-128-1) was recently linked to the evolutionary adaptation to famine and identified as a thrifty microRNA that controls energy expenditure, contributing to obesity and impaired glucose metabolism.

OBJECTIVES

We investigated whether circulating miR-128-1-5p and its temporal changes in response to weight-loss diet interventions were related to regulating insulin resistance, adiposity, and energy expenditure in adults with overweight and obesity. We also examined whether habitual physical activity (PA) and different macronutrient intakes modified associations of changes in miR-128-1-5p with improved metabolic outcomes.

METHODS

This study included 495 adults who consumed weight-loss diets with different macronutrient intakes. Circulating levels of miR-128-1-5p were assessed at baseline and 6 mo after the interventions. Outcome measurements included changes in insulin resistance HOMA-IR, adiposity, and resting energy expenditure.

RESULTS

We observed significant relations between circulating miR-128-1-5p and the positive selection signals at the 2q21.3 locus assessed by the single nucleotide polymorphisms rs1446585 and rs4988235. Higher miR-128-1-5p levels were associated with greater HOMA-IR (β per 1 SD: 0.08 [SE 0.03]; P = 0.009), waist circumference (β, 1.16 [0.55]; P = 0.036), whole-body total % fat mass (β, 0.75 [0.30]; P = 0.013), and REE (β, 23 [11]; P = 0.037). In addition, higher miR-128-1-5p level was related to lower total PA index (β, -0.23 [0.07]; P = 0.001) and interacted with PA (Pinteraction < 0.05) on changes in HOMA-IR and adiposity. We found that greater increases in miR-128-1-5p levels after the interventions were associated with lesser improvements in HOMA-IR and adiposity in participants with no change/decreases in PA. Furthermore, we found that dietary fat (Pinteraction = 0.027) and protein (Pinteraction= 0.055) intakes modified relations between changes in miR-128-1-5p and REE.

CONCLUSIONS

Circulating thrifty miRNA was linked to regulating body fat, insulin resistance, and energy metabolism. Temporal changes in circulating miR-128-1-5p were associated with better weight-loss outcomes during the interventions; habitual PA and dietary macronutrient intake may modify such relations. This trial was registered at clinicaltrials.gov as NCT00072995.

Effects of exercise on irisin in subjects with overweight or obesity. A systematic review of clinical studies

Introduction

Irisin is an adipomyokine involved in white adipose tissue browning, therefore, could be a key protein in metabolic health. However, exercise effects on irisin in subjects with overweight and/or obesity are conflicting. Therefore, this systematic review aims to search and analyse the literature available on this topic. From three databases: PubMed, ScienceDirect, and Medline, clinical studies published between 2010 and 2021 were considered. From 134 found, 14 studies were included. Only six reported plasma increases after exercise (~1.2 to 3-fold from pre-exercise levels). In addition, only 1 reported significant increases in skeletal muscle irisin mRNA levels (~2-fold). Also, irisin was measured from subcutaneous adipose tissue and saliva, where a ~2-fold increase in its protein levels was found in the latter. Exercise seems to increase the circulatory concentrations of irisin in subjects with overweight or obesity. However, this response is highly variable, therefore, a more integrative approach is urgently needed.

Brown adipose tissue human biomarkers: Which one fits best? A narrative review

Adipose tissue (AT) is an endocrine metabolically dynamic active tissue that plays a central role in the systemic energy balance and metabolic regulation. Brown AT represents approximately 1% of adult human AT, with an energy-burning function that uses fat to create heat. Brown AT activity was measured using 18F-fluorodeoxyglucose positron emission tomography/computed tomography. It has been shown that cold exposure could promote brown AT activation. However, many factors, such as aging and body mass index, may interfere with this activity. Many authors have discussed the role of factors specifically secreted by the AT in response to cold exposure. The aim of this review is to properly understand the effects of cold on AT and biomarkers and their possible application in rehabilitation medicine. A comprehensive literature review was performed to identify published studies regarding biomarkers of cold effects on Brown AT searching the following databases: PubMed, Science Direct, and Web of Science, from 2012 to 2022. After evaluation of the inclusion and exclusion criteria, 9 studies were included in this review. We reported the overall influence of cold exposure on brown AT activity, its related biomarkers, and metabolism, demonstrating that the therapeutic role of cold exposure needs to be better standardized. From our data, it is important to design proper clinical trials because most cold applied protocols lack a common and homogeneous methodology.

Chrononutrition-When We Eat Is of the Essence in Tackling Obesity

Obesity is a chronic and relapsing public health problem with an extensive list of associated comorbidities. The worldwide prevalence of obesity has nearly tripled over the last five decades and continues to pose a serious threat to wider society and the wellbeing of future generations. The pathogenesis of obesity is complex but diet plays a key role in the onset and progression of the disease. The human diet has changed drastically across the globe, with an estimate that approximately 72% of the calories consumed today come from foods that were not part of our ancestral diets and are not compatible with our metabolism. Additionally, multiple nutrient-independent factors, e.g., cost, accessibility, behaviours, culture, education, work commitments, knowledge and societal set-up, influence our food choices and eating patterns. Much research has been focused on 'what to eat' or 'how much to eat' to reduce the obesity burden, but increasingly evidence indicates that 'when to eat' is fundamental to human metabolism. Aligning feeding patterns to the 24-h circadian clock that regulates a wide range of physiological and behavioural processes has multiple health-promoting effects with anti-obesity being a major part. This article explores the current understanding of the interactions between the body clocks, bioactive dietary components and the less appreciated role of meal timings in energy homeostasis and obesity.

Potential Implications of Exercise Training on Pannexin Expression and Function

Pannexins (PANX1, 2, 3) are channel-forming glycoproteins that are expressed throughout the cardiovascular and musculoskeletal system. The canonical function of these proteins is to release nucleotides that act as purinergic signalling at the cell membrane or Ca2+ channels at the endoplasmic reticulum membrane. These two forms of signalling are essential for autocrine and paracrine signalling in health, and alterations in this signalling have been implicated in the pathogenesis of many diseases. Many musculoskeletal and cardiovascular diseases are largely the result of a lack of physical activity which causes altered gene expression. Considering exercise training has been shown to alter a wide array of gene expression in musculoskeletal tissues, understanding the interaction between exercise training, gene function and expression in relevant diseases is warranted. With regards to pannexins, multiple publications have shown that exercise training can influence pannexin expression and may influence the significance of its function in certain diseases. This review further discusses the potential interaction between exercise training and pannexin biology in relevant tissues and disease models. We propose that exercise training in relevant animal and human models will provide a more comprehensive understanding of the implications of pannexin biology in disease.

Meteorin-like protein (Metrnl): A metabolic syndrome biomarker and an exercise mediator

Metrnl is a secreted protein able to activate different intracellular signaling pathways in adipocytes, macrophages, myocytes and cardiomyocytes with physiological effects of the browning of white adipose tissue (BWT), insulin sensitivity, inflammation inhibition, skeletal muscle regeneration and heart protection. Shown to be regulated by obesity, diabetes, caloric restriction, weight loss and heart diseases, Metrnl is definitely involved in metabolic turbulences, and may play roles in metabolic syndrome (MetS). However, due to the conflicting data yielded, Metrnl is still far from clinical application as a diagnostic and/or a therapeutic agent or even a therapeutic target in MetS-related diseases such as type 2 diabetes (T2D) and obesity. Nevertheless, blood Metrnl levels as well as Metrnl as a cardiokine have been reported to play cardioprotective roles against heart diseases. Considering the established metabolic and anti-inflammatory hallmarks, exercise-induced Metrnl (as a myokine) is regarded as an exercise mediator in improving obesity-induced complications such as insulin resistance, T2D and inflammation. Besides, due to its healing role in muscle damage, Metrnl is also a potential therapeutic candidate to enhance regeneration with ageing or other inflammatory myopathies like Duchenne muscular dystrophy (DMD). Therefore, there are still many exercise-related questions unanswered on Metrnl, such as Metrnl-mediated fat browning in humans, exercise effects on heart Metrnl production and secretion and the effects of other exercise-induced skeletal muscle stressors like hypoxia and oxidative in Metrnl production other than exercise-induced muscle damage.

Combined effects of voluntary running and liraglutide on glucose homeostasis, fatty acid composition of brown adipose tissue phospholipids, and white adipose tissue browning in db/db mice

There is a potential therapeutic application targeting brown adipose tissue (BAT). Either voluntary running or liraglutide increases the thermogenesis of BAT in type 2 diabetes mellitus, but their combined effect is not yet clarified. Male leptin receptor-deficient db/db diabetic mice (n = 24) were randomly divided into voluntary running, liraglutide, voluntary running + liraglutide, and control groups (n = 6/group). Normal male C57 mice were the negative control (n = 6). Fasting blood glucose was monitored every week, plasma insulin and lipid profiles were analyzed, and thermogenic protein expression in BAT and white adipose tissue (WAT) were analyzed by the western blot. A total of 128 metabolites associated with phosphatidylcholines, phosphatidylethanolamines, sphingomyelins, and ceramides were targeted in BAT. Compared to the control group, voluntary running or liraglutide treatment significantly lowered the blood glucose and increased the insulin level; the combined group showed a better effect than liraglutide alone. Hence, the combined treatment showed an enhanced hypoglycemic effect. Uncoupling protein 1 (UCP1) and OXPHOS protein expression in BAT and UCP1 in WAT were significantly increased after exercise training and liraglutide treatment. However, BAT metabolomics showed that compared to the control mice, nine fatty acids increased in the exercise group, six increased in the liraglutide group, and only three increased in the combined group. These results may suggest a higher hypoglycemic effect and the activation of BAT and WAT browning in the combined group.

Exercise, Mitohormesis, and Mitochondrial ORF of the 12S rRNA Type-C (MOTS-c)

Low levels of mitochondrial stress are beneficial for organismal health and survival through a process known as mitohormesis. Mitohormetic responses occur during or after exercise and may mediate some salutary effects of exercise on metabolism. Exercise-related mitohormesis involves reactive oxygen species production, mitochondrial unfolded protein response (UPRmt), and release of mitochondria-derived peptides (MDPs). MDPs are a group of small peptides encoded by mitochondrial DNA with beneficial metabolic effects. Among MDPs, mitochondrial ORF of the 12S rRNA type-c (MOTS-c) is the most associated with exercise. MOTS-c expression levels increase in skeletal muscles, systemic circulation, and the hypothalamus upon exercise. Systemic MOTS-c administration increases exercise performance by boosting skeletal muscle stress responses and by enhancing metabolic adaptation to exercise. Exogenous MOTS-c also stimulates thermogenesis in subcutaneous white adipose tissues, thereby enhancing energy expenditure and contributing to the anti-obesity effects of exercise training. This review briefly summarizes the mitohormetic mechanisms of exercise with an emphasis on MOTS-c.

Aerobic exercise for eight weeks provides protective effects towards liver and cardiometabolic health and adipose tissue remodeling under metabolic stress for one week: A study in mice

BACKGROUND

The relationship between exercise training and health benefits is under thorough investigation. However, the effects of exercise training on the maintenance of metabolic health are unclear.

METHODS

Our experimental design involved initial exercise training followed by a high-fat diet (HFD) challenge. Eight-week-old male was trained under voluntary wheel running aerobic exercise for eight weeks to determine the systemic metabolic changes induced by exercise training and whether such changes persisted even after discontinuing exercise. The mice were given either a normal chow diet (NCD) or HFD ad libitum for one week after discontinuation of exercise (CON-NCD, n = 29; EX-NCD, n = 29; CON-HFD, n = 30; EX-HFD, n = 31).

RESULTS

Our study revealed that metabolic stress following the transition to an HFD in mice that discontinued training failed to reverse the aerobic exercise training-induced improvement in metabolism. We report that the mice subjected to exercise training could better counteract weight gain, adipose tissue hypertrophy, insulin resistance, fatty liver, and mitochondrial dysfunction in response to an HFD compared with untrained mice. This observation could be attributed to the fact that exercise enhances the browning of white fat, whole-body oxygen uptake, and heat generation. Furthermore, we suggest that the effects of exercise persist due to PPARα-FGF21-FGFR1 mechanisms, although additional pathways cannot be excluded and require further research. Although our study suggests the preventive potential of exercise, appropriate human trials are needed to demonstrate the efficacy in subjects who cannot perform sustained exercise; this may provide an important basis regarding human health.

Exercise, Physical Activity, and Cardiometabolic Health: Pathophysiologic Insights

Physical activity and its sustained and purposeful performance-exercise-promote a broad and diverse set of metabolic and cardiovascular health benefits. Regular exercise is the most effective way to improve cardiorespiratory fitness, a measure of one's global cardiovascular, pulmonary and metabolic health, and one of the strongest predictors of future health risk. Here, we describe how exercise affects individual organ systems related to cardiometabolic health, including the promotion of insulin and glucose homeostasis through improved efficiency in skeletal muscle glucose utilization and enhanced insulin sensitivity; beneficial changes in body composition and adiposity; and improved cardiac mechanics and vascular health. We subsequently identify knowledge gaps that remain in exercise science, including heterogeneity in exercise responsiveness. While the application of molecular profiling technologies in exercise science has begun to illuminate the biochemical pathways that govern exercise-induced health promotion, much of this work has focused on individual organ systems and applied single platforms. New insights into exercise-induced secreted small molecules and proteins that impart their effects in distant organs ("exerkines") highlight the need for an integrated approach towards the study of exercise and its global effects; efforts that are ongoing.

Distinct Effects of High-Fat and High-Phosphate Diet on Glucose Metabolism and the Response to Voluntary Exercise in Male Mice

The prevalence of metabolic diseases is rapidly increasing and a principal contributor to this is diet, including increased consumption of energy-rich foods and foods with added phosphates. Exercise is an effective therapeutic approach to combat metabolic disease. While exercise is effective to combat the detrimental effects of a high-fat diet on metabolic health, the effects of exercise on a high-phosphate diet have not been thoroughly investigated. Here, we investigated the effects of a high-fat or high-phosphate diet in the presence or absence of voluntary exercise on metabolic function in male mice. To do this, mice were fed a low-fat, normal-phosphate diet (LFPD), a high-phosphate diet (HPD) or a high-fat diet (HFD) for 6 weeks and then subdivided into either sedentary or exercised (housed with running wheels) for an additional 8 weeks. An HFD severely impaired metabolic function in mice, increasing total fat mass and worsening whole-body glucose tolerance, while HPD did not induce any notable effects on glucose metabolism. Exercise reverted most of the detrimental metabolic adaptations induced by HFD, decreasing total fat mass and restoring whole-body glucose tolerance and insulin sensitivity. Interestingly, voluntary exercise had a similar effect on LFPD and HPD mice. These data suggest that a high-phosphate diet does not significantly impair glucose metabolism in sedentary or voluntary exercised conditions.

Batokines: Mediators of Inter-Tissue Communication (a Mini-Review)

PURPOSE OF REVIEW

This review highlights aspects of brown adipose tissue (BAT) communication with other organ systems and how BAT-to-tissue cross-talk could help elucidate future obesity treatments.

RECENT FINDINGS

Until recently, research on BAT has focused mainly on its thermogenic activity. New research has identified an endocrine/paracrine function of BAT and determined that many BAT-derived molecules, termed "batokines," affect the physiology of a variety of organ systems and cell types. Batokines encompass a variety of signaling molecules including peptides, metabolites, lipids, or microRNAs. Recent studies have noted significant effects of batokines on physiology as it relates whole-body metabolism and cardiac function. This review will discuss batokines and other BAT processes that affect the liver, cardiovascular system, skeletal muscle, immune cells, and brown and white adipose tissue. Brown adipose tissue has a crucial secretory function that plays a key role in systemic physiology.

Exercise-induced changes on exerkines that might influence brown adipose tissue metabolism in young sedentary adults

In rodents, exercise alters the plasma concentration of exerkines that regulate white adipose tissue (WAT) browning or brown adipose tissue (BAT) metabolism. This study aims to analyse the acute and chronic effect of exercise on the circulating concentrations of 16 of these exerkines in humans. Ten young sedentary adults (6 female) performed a maximum walking effort test and a resistance exercise session. The plasma concentration of 16 exerkines was assessed before, and 3, 30, 60, and 120 minutes after exercise. Those exerkines modified by exercise were additionally measured in another 28 subjects (22 women). We also measured the plasma concentrations of the exerkines before and after a 24-week exercise program (endurance + resistance; 3-groups: control, moderate-intensity and vigorous-intensity) in 110 subjects (75 women). Endurance exercise acutely increased the plasma concentration of lactate, norepinephrine, brain-derived neurotrophic factor, interleukin 6, and follistatin-like protein 1 (3 minutes after exercise), and musclin and fibroblast growth factor 21 (30 and 60 minutes after exercise), decreasing the plasma concentration of leptin (30 minutes after exercise). Adiponectin, atrial natriuretic peptide (ANP), β-aminoisobutyric acid, meteorin-like, follistatin, pro-ANP, irisin and myostatin were not modified or not detectable. The resistance exercise session increased the plasma concentration of lactate 3 minutes after exercise. Chronic exercise did not alter the plasma concentration of these exerkines. In sedentary young adults, acute endurance exercise releases to the bloodstream exerkines that regulate BAT metabolism and WAT browning. In contrast, neither a low-volume resistance exercise session nor a 24-week training program modified plasma levels of these molecules.Trial registration: ClinicalTrials.gov identifier: NCT02365129..

Physical activity ameliorates the function of organs via adipose tissue in metabolic diseases

Adipose tissue is a dynamic organ in the endocrine system that can connect organs by secreting molecules and bioactive. Hence, adipose tissue really plays a pivotal role in regulating metabolism, inflammation, energy homeostasis, and thermogenesis. Disruption of hub bioactive molecules secretion such as adipokines leads to dysregulate metabolic communication between adipose tissue and other organs in non-communicable disorders. Moreover, a sedentary lifestyle may be a risk factor for adipose tissue function. Physical inactivity leads to fat tissue accumulation and promotes obesity, Type 2 diabetes, cardiovascular disease, neurodegenerative disease, fatty liver, osteoporosis, and inflammatory bowel disease. On the other hand, physical activity may ameliorate and protect the body against metabolic disorders, triggering thermogenesis, metabolism, mitochondrial biogenesis, β-oxidation, and glucose uptake. Furthermore, physical activity provides an inter-organ association and cross-talk between different tissues by improving adipose tissue function, reprogramming gene expression, modulating molecules and bioactive factors. Also, physical activity decreases chronic inflammation, oxidative stress and improves metabolic features in adipose tissue. The current review focuses on the beneficial effect of physical activity on the cardiovascular, locomotor, digestive, and nervous systems. In addition, we visualize protein-protein interactions networks between hub proteins involved in dysregulating metabolic induced by adipose tissue.

The effects of neurogranin knockdown on SERCA pump efficiency in soleus muscles of female mice fed a high fat diet

The sarco(endo)plasmic reticulum Ca²⁺ ATPase (SERCA) pump is responsible for the transport of Ca²⁺ from the cytosol into the sarcoplasmic reticulum at the expense of ATP, making it a regulator of both muscle relaxation and muscle-based energy expenditure. Neurogranin (Ng) is a small protein that negatively regulates calcineurin signaling. Calcineurin is Ca²⁺/calmodulin dependent phosphatase that promotes the oxidative fibre type in skeletal muscle and regulates muscle-based energy expenditure. A recent study has shown that calcineurin activation reduces SERCA Ca²⁺ transport efficiency, ultimately raising energy expenditure. Since the biomedical view of obesity states that it arises as an imbalance between energy intake and expenditure which favors the former, we questioned whether heterozygous Ng deletion (Ng^+/- ) would reduce SERCA efficiency and increase energy expenditure in female mice fed a high-fat diet (HFD). Young (3-4-month-old) female wild type (WT) and Ng^+/- mice were fed a HFD for 12 weeks with their metabolic profile being analyzed using metabolic cages and DXA scanning, while soleus SERCA efficiency was measured using SERCA specific Ca²⁺ uptake and ATPase activity assays. Ng^+/- mice showed significantly less cage ambulation compared to WT mice but this did not lead to any added weight gain nor changes in daily energy expenditure, glucose or insulin tolerance despite a similar level of food intake. Furthermore, we observed significant reductions in SERCA's apparent coupling ratio which were associated with significant reductions in SERCA1 and phospholamban content. Thus, our results show that Ng regulates SERCA pump efficiency, and future studies should further investigate the potential cellular mechanisms.

Interactive effects of aging and aerobic capacity on energy metabolism-related metabolites of serum, skeletal muscle, and white adipose tissue

Aerobic capacity is a strong predictor of longevity. With aging, aerobic capacity decreases concomitantly with changes in whole body metabolism leading to increased disease risk. To address the role of aerobic capacity, aging, and their interaction on metabolism, we utilized rat models selectively bred for low and high intrinsic aerobic capacity (LCRs/HCRs) and compared the metabolomics of serum, muscle, and white adipose tissue (WAT) at two time points: Young rats were sacrificed at 9 months of age, and old rats were sacrificed at 21 months of age. Targeted and semi-quantitative metabolomics analysis was performed on the ultra-pressure liquid chromatography tandem mass spectrometry (UPLC-MS) platform. The effects of aerobic capacity, aging, and their interaction were studied via regression analysis. Our results showed that high aerobic capacity is associated with an accumulation of isovalerylcarnitine in muscle and serum at rest, which is likely due to more efficient leucine catabolism in muscle. With aging, several amino acids were downregulated in muscle, indicating more efficient amino acid metabolism, whereas in WAT less efficient amino acid metabolism and decreased mitochondrial β-oxidation were observed. Our results further revealed that high aerobic capacity and aging interactively affect lipid metabolism in muscle and WAT, possibly combating unfavorable aging-related changes in whole body metabolism. Our results highlight the significant role of WAT metabolism for healthy aging.

Human Brown Adipose Tissue and Metabolic Health: Potential for Therapeutic Avenues

Obesity-associated metabolic abnormalities comprise a cluster of conditions including dyslipidemia, insulin resistance, diabetes and cardiovascular diseases that has affected more than 650 million people all over the globe. Obesity results from the accumulation of white adipose tissues mainly due to the chronic imbalance of energy intake and energy expenditure. A variety of approaches to treat or prevent obesity, including lifestyle interventions, surgical weight loss procedures and pharmacological approaches to reduce energy intake and increase energy expenditure have failed to substantially decrease the prevalence of obesity. Brown adipose tissue (BAT), the primary source of thermogenesis in infants and small mammals may represent a promising therapeutic target to treat obesity by promoting energy expenditure through non-shivering thermogenesis mediated by mitochondrial uncoupling protein 1 (UCP1). Since the confirmation of functional BAT in adult humans by several groups, approximately a decade ago, and its association with a favorable metabolic phenotype, intense interest on the significance of BAT in adult human physiology and metabolic health has emerged within the scientific community to explore its therapeutic potential for the treatment of obesity and metabolic diseases. A substantially decreased BAT activity in individuals with obesity indicates a role for BAT in the setting of human obesity. On the other hand, BAT mass and its prevalence correlate with lower body mass index (BMI), decreased age and lower glucose levels, leading to a lower incidence of cardio-metabolic diseases. The increased cold exposure in adult humans with undetectable BAT was associated with decreased body fat mass and increased insulin sensitivity. A deeper understanding of the role of BAT in human metabolic health and its interrelationship with body fat distribution and deciphering proper strategies to increase energy expenditure, by either increasing functional BAT mass or inducing white adipose browning, holds the promise for possible therapeutic avenues for the treatment of obesity and associated metabolic disorders.

New Insights into Molecular Mechanisms Mediating Adaptation to Exercise; A Review Focusing on Mitochondrial Biogenesis, Mitochondrial Function, Mitophagy and Autophagy

Exercise itself is fundamental for good health, and when practiced regularly confers a myriad of metabolic benefits in a range of tissues. These benefits are mediated by a range of adaptive responses in a coordinated, multi-organ manner. The continued understanding of the molecular mechanisms of action which confer beneficial effects of exercise on the body will identify more specific pathways which can be manipulated by therapeutic intervention in order to prevent or treat various metabolism-associated diseases. This is particularly important as exercise is not an available option to all and so novel methods must be identified to confer the beneficial effects of exercise in a therapeutic manner. This review will focus on key emerging molecular mechanisms of mitochondrial biogenesis, autophagy and mitophagy in selected, highly metabolic tissues, describing their regulation and contribution to beneficial adaptations to exercise.

Exercise induces favorable metabolic changes in white adipose tissue preventing high-fat diet obesity

Diet and/or exercise are cost effective interventions to treat obesity. However, it is unclear if the type of exercise undertaken can prevent the onset of obesity and if it can act through different effects on fat depots. In this study we did not allow obesity to develop so we commenced the high-fat diet (HFD) and exercise programs concurrently and investigated the effect of endurance exercise (END) and high-intensity interval training (HIIT) on changes in cellular adipogenesis, thermogenesis, fibrosis, and inflammatory markers in three different fat depots, on a HFD and a chow diet. This was to assess the effectiveness of exercise to prevent the onset of obesity-induced changes. Mice fed with chow or HFD (45% kcal fat) were trained and performed either END or HIIT for 10 weeks (3 x 40 min sessions/week). In HFD mice, both exercise programs significantly prevented the increase in body weight (END: 17%, HIIT: 20%), total body fat mass (END: 46%, HIIT: 50%), increased lean mass as a proportion of body weight (Lean mass/BW) by 14%, and improved insulin sensitivity by 22%. Further evidence of the preventative effect of exercise was seen significantly decreased markers for adipogenesis, inflammation, and extracellular matrix accumulation in both subcutaneous adipose tissue (SAT) and epididymal adipose tissue (EPI). In chow, no such marked effects were seen with both the exercise programs on all the three fat depots. This study establishes the beneficial effect of both HIIT and END exercise in preventing metabolic deterioration, collagen deposition, and inflammatory responses in fat depots, resulting in an improved whole body insulin resistance in HFD mice.

The Effects of High-Protein Diet and Resistance Training on Glucose Control and Inflammatory Profile of Visceral Adipose Tissue in Rats

High-protein diets (HPDs) are widely accepted as a way to stimulate muscle protein synthesis when combined with resistance training (RT). However, the effects of HPDs on adipose tissue plasticity and local inflammation are yet to be determined. This study investigated the impact of HPDs on glucose control, adipocyte size, and epididymal adipose inflammatory biomarkers in resistance-trained rats. Eighteen Wistar rats were randomly assigned to four groups: normal-protein (NPD; 17% protein total dietary intake) and HPD (26.1% protein) without RT and NPD and HPD with RT. Trained groups received RT for 12 weeks with weights secured to their tails. Glucose and insulin tolerance tests, adipocyte size, and an array of cytokines were determined. While HPD without RT induced glucose intolerance, enlarged adipocytes, and increased TNF-α, MCP-1, and IL1-β levels in epididymal adipose tissue (p < 0.05), RT diminished these deleterious effects, with the HPD + RT group displaying improved blood glucose control without inflammatory cytokine increases in epididymal adipose tissue (p < 0.05). Furthermore, RT increased glutathione expression independent of diet (p < 0.05). RT may offer protection against adipocyte hypertrophy, pro-inflammatory states, and glucose intolerance during HPDs. The results highlight the potential protective effects of RT to mitigate the maladaptive effects of HPDs.

The Protective Effects of Sulforaphane on High-Fat Diet-Induced Obesity in Mice Through Browning of White Fat

Background: Sulforaphane (SFN), an isothiocyanate naturally occurring in cruciferous vegetables, is a potent indirect antioxidant and a promising agent for the control of metabolic disorder disease. The glucose intolerance and adipogenesis induced by diet in rats was inhibited by SFN. Strategies aimed at induction of brown adipose tissue (BAT) could be a potentially useful way to against obesity. However, in vivo protective effect of SFN against obesity by browning white adipocyte has not been reported. Our present study is aimed at evaluation the efficacy of the SFN against the high-fat induced-obesity mice and investigating the potential mechanism.

Methods: High-Fat Diet-induced obese female C57BL/6 mice were intraperitoneally injected with SFN (10 mg/kg) daily. Body weight was recorded every 3 days. 30 days later, glucose tolerance test (GTT) and insulin tolerance test (ITT) were performed. At the end of experiment, fat mass were measured and the adipogenesis as well as browning associated genes expression in white adipose tissue (WAT) were determined by RT-qPCR and western blot. Histological examination of the adipose tissue samples were carried out with hematoxylin–eosin (HE) staining and immunofluorescence staining method. In vitro, pre-adipocytes C3H10T1/2 were treated with SFN to investigate the direct effects on adipogenesis.

Results: SFN suppressed HFD-induced body weight gain and reduced the size of fat cells in mice. SFN suppressed the expression of key genes in adipogenesis, inhibited lipid accumulation in C3H10T1/2 cells, increased the expression of brown adipocyte-specific markers and mitochondrial biogenesis in vivo and in vitro, and decreased cellular and mitochondrial oxidative stress. These results suggested that SFN, as a nutritional factor, has great potential role in the battle against obesity by inducing the browning of white fat.

Conclusion: SFN could significantly decrease the fat mass, and improve glucose metabolism and increase insulin sensitivity of HFD-induced obese mice by promoting the browning of white fat and enhancing the mitochondrial biogenesis in WAT. Our study proves that SFN could serve as a potential medicine in anti-obesity and related diseases.

The Role of Exercise, Diet, and Cytokines in Preventing Obesity and Improving Adipose Tissue

The prevalence of obesity continues to rise worldwide despite evidence-based public health recommendations. The promise to adopt a healthy lifestyle is increasingly important for tackling this global epidemic. Calorie restriction or regular exercise or a combination of the two is accepted as an effective strategy in preventing or treating obesity. Furthermore, the benefits conferred by regular exercise to overcome obesity are attributed not only to reduced adiposity or reduced levels of circulating lipids but also to the proteins, peptides, enzymes, and metabolites that are released from contracting skeletal muscle or other organs. The secretion of these molecules called cytokines in response to exercise induces browning of white adipose tissue by increasing the expression of brown adipocyte-specific genes within the white adipose tissue, suggesting that exercise-induced cytokines may play a significant role in preventing obesity. In this review, we present research-based evidence supporting the effects of exercise and various diet interventions on preventing obesity and adipose tissue health. We also discuss the interplay between adipose tissue and the cytokines secreted from skeletal muscle and other organs that are known to affect adipose tissue and metabolism.

Mirabegron: The most promising adipose tissue beiging agent

Accumulation of white adipose tissue (WAT) underlies the obesity epidemic, leading to current therapeutic techniques that are being investigated for their ability to activate/“beige” this tissue. Adipose tissue (AT) beiging has been reported through intermittent cold exposure (CE), exercise, and β3‐Adrenergic Receptor (β3AR) agonists. But how AT beiging can help in the treatment of metabolic disorders like obesity and type 2 diabetes (T2D) remains largely unexplored. This review summarizes recent research on the use of β3AR agonist, mirabegron (Myrbetriq®), in stimulating beiging in AT. Researchers have only recently been able to determine the optimal therapeutic dose of mirabegron for inducing beiging in subcutaneous/ inguinal WAT, where the benefits of AT activation are evident without the undesired cardiovascular side effects. To determine whether the effects that mirabegron elicits are metabolically beneficial, a comparison of the undisputed findings resulting from intermittent CE‐induced beiging and the disputed findings from exercise‐induced beiging was conducted. Given the recent in vivo animal and clinical studies, the understanding of how mirabegron can be metabolically beneficial for both lean and obese individuals is more clearly understood. These studies have demonstrated that circulating adipokines, glucose metabolism, and lipid droplet (LD) size are all positively affected by mirabegron administration. Recent studies have also demonstrated that mirabegron has similar outcomes to intermittent CE and displays more direct evidence for beiging than those produced with exercise. With these current findings, mirabegron is considered the most promising and safest β3AR agonist currently available that has the potential to be used in the therapeutic treatment of metabolic disorders, and future studies into its interaction with different conditions may prove to be useful as part of a treatment plan in combination with a healthy diet and exercise.

Sigma-1 receptor ablation impedes adipocyte-like differentiation of mouse embryonic fibroblasts

The sigma-1 receptor (Sig1R) is a unique ligand-operated endoplasmic reticulum (ER) protein without any mammalian homolog. It has long been a pharmacological target for intervention of psychiatric disorders, and recently garnered refreshed interest for its neuroprotective potential. Though reported to modulate various intracellular events, its influence on cell identity is little known. We explored a role for Sig1R in adipocyte differentiation. We induced adipogenic differentiation of mouse embryonic fibroblasts (MEFs) with a differentiation medium. MEFs were isolated from Sigmar1-/- and Sigmar1+/+ mice. The induced adipocyte-like phenotype was detected through Western blots of master transcription factors (PPARγ, CEBPA, SREBP1, SREBP2), lipogenic proteins (FABP4, ACC1, ACAT2), and Oil-Red-O staining of lipids. We found that the induced upregulation of these proteins and lipid accumulation were severely mitigated in Sigmar1-/- (vs Sigmar1+/+) MEFs. Sig1R activation with a selective agonist (PRE084) increased Sig1R protein and further enhanced the induced adipocyte-like phenotype in Sigmar1+/+ MEFs. We also determined mouse body weight gain induced by high-fat diet for 6 months, which was impeded in Sigmar1-/- (vs Sigmar1+/+) male mice. In summary, genetic ablation of Sig1R impairs, and agonist activation of Sig1R enhances adipocyte-like phenotype of induced MEFs. In vivo, Sig1R ablation impedes the body weight gain of male mice on high-fat diet. This study warrants further investigation of a previously unrecognized role for Sig1R in adipocyte differentiation.

Pitfalls and challenges of the purinergic signaling cascade in obesity

Obesity is a worldwide health problem which have reached pandemic proportions, now also including low and middle-income countries. Excessive or abnormal fat deposition in the abdomen especially in the visceral compartment is tightly associated with a high metabolic risk for arterial hypertension, type II diabetes, cardiovascular diseases, musculoskeletal disorders (especially articular degeneration) and some cancers. Contrariwise, accumulation of fat in the subcutaneous compartment has been associated with a neutral metabolic impact, favoring a lower risk of insulin resistance. Obesity results more often from an avoidable imbalance between food consumption and energy expenditure. There are several recommended strategies for dealing with obesity, including pharmacological therapies, but their success remains incomplete and may not compensate the associated adverse effects. Purinergic signaling operated by ATP and its metabolite, adenosine, has attracted increasing attention in obesity. The extracellular levels of purines often reflect the energy status of a given cell population. Adenine nucleotides and nucleosides fine tuning control adipogenesis and mature adipocytes function via the activation of P2 and P1 purinoceptors, respectively. These features make the purinergic signaling cascade a putative target for therapeutic intervention in obesity and related metabolic syndromes. There are, however, gaps in our knowledge regarding the role of purines in adipocyte precursors differentiation and mature adipocytes functions, as well as their impact among distinct adipose tissue deposits (e.g. white vs. brown, visceral vs. subcutaneous), which warrants further investigations before translation to clinical trials can be made.