Differential sympathetic outflow to adipose depots is required for visceral fat loss in response to calorie restriction

Multi-Organ Increase in Norepinephrine Levels after Central Leptin Administration and Diet-Induced Obesity

Autonomic innervation is important to regulate homeostasis in every organ of the body. The sympathetic nervous system controls several organs associated with metabolism and reproduction, including adipose tissue, the liver, and the ovaries. The sympathetic nervous system is controlled within the central nervous system by neurons located in the hypothalamus, which in turn are regulated by hormones like leptin. Leptin action in the hypothalamus leads to increased sympathetic activity in the adipose tissue. In this short report, we propose that leptin action in the brain also controls the sympathetic innervation of other organs like the liver and the ovary. We performed two experiments: We performed an intracerebroventricular (ICV) injection of leptin and measured norepinephrine levels in several organs, and we used a validated model of overnutrition and obesity to evaluate whether an increase in leptin levels coexists with high levels of norepinephrine in the liver and ovaries. Norepinephrine was measured by ELISA in adipose tissue and by HPLC-EC in other tissues. Leptin was measured by ELISA. We found that the ICV injection of leptin increases norepinephrine levels in several organs, including the liver and ovaries. Also, we found that diet-induced obesity leads to an increase in leptin levels while inducing an increase in norepinephrine levels in the liver and ovaries. Finally, since hyperactivity of the sympathetic nervous system is observed both in non-alcoholic fatty liver disease and polycystic ovary syndrome, we think that an increase in norepinephrine levels induced by hyperleptinemia could be involved in the pathogenesis of both diseases.

High-intensity interval training improves fatty infiltration in the rotator cuff through the β3 adrenergic receptor in mice

Aims

Rotator cuff muscle atrophy and fatty infiltration affect the clinical outcomes of rotator cuff tear patients. However, there is no effective treatment for fatty infiltration at this time. High-intensity interval training (HIIT) helps to activate beige adipose tissue. The goal of this study was to test the role of HIIT in improving muscle quality in a rotator cuff tear model via the β3 adrenergic receptor (β3AR).

Methods

Three-month-old C57BL/6 J mice underwent a unilateral rotator cuff injury procedure. Mice were forced to run on a treadmill with the HIIT programme during the first to sixth weeks or seventh to 12th weeks after tendon tear surgery. To study the role of β3AR, SR59230A, a selective β3AR antagonist, was administered to mice ten minutes before each exercise through intraperitoneal injection. Supraspinatus muscle, interscapular brown fat, and inguinal subcutaneous white fat were harvested at the end of the 12th week after tendon tear and analyzed biomechanically, histologically, and biochemically.

Results

Histological analysis of supraspinatus muscle showed that HIIT improved muscle atrophy, fatty infiltration, and contractile force compared to the no exercise group. In the HIIT groups, supraspinatus muscle, interscapular brown fat, and inguinal subcutaneous white fat showed increased expression of tyrosine hydroxylase and uncoupling protein 1, and upregulated the β3AR thermogenesis pathway. However, the effect of HIIT was not present in mice injected with SR59230A, suggesting that HIIT affected muscles via β3AR.

Conclusion

HIIT improved supraspinatus muscle quality and function after rotator cuff tears by activating systemic sympathetic nerve fibre near adipocytes and β3AR.

Neurobiology, Stem Cell Biology, and Immunology: An Emerging Triad for Understanding Tissue Homeostasis and Repair

The peripheral nervous system (PNS) endows animals with the remarkable ability to sense and respond to a dynamic world. Emerging evidence shows the PNS also participates in tissue homeostasis and repair by integrating local changes with organismal and environmental changes. Here, we provide an in-depth summary of findings delineating the diverse roles of peripheral nerves in modulating stem cell behaviors and immune responses under steady-state conditions and in response to injury and duress, with a specific focus on the skin and the hematopoietic system. These examples showcase how elucidating neuro-stem cell and neuro-immune cell interactions provides a conceptual framework that connects tissue biology and local immunity with systemic bodily changes to meet varying demands. They also demonstrate how changes in these interactions can manifest in stress, aging, cancer, and inflammation, as well as how these findings can be harnessed to guide the development of new therapeutics.

Sex-specific differences in metabolic outcomes after sleeve gastrectomy and intermittent fasting in obese middle-aged mice

Despite the high prevalence of obesity among middle-aged subjects, it is unclear if sex differences in middle age affect the metabolic outcomes of obesity therapies. Accordingly, in this study, middle-aged obese female and male mice were randomized to one of three groups: sleeve gastrectomy (SG), sham surgery ad libitum (SH-AL), or sham surgery with weight matching to SG through intermittent fasting with calorie restriction (SH-IF). Comprehensive measures of energy and glucose homeostasis, including energy intake, body weight, energy expenditure, glucose and insulin tolerance, and interscapular brown adipose tissue (iBAT) sympathetic innervation density were obtained. At the end of 8 wk, SG and SH-IF females had better metabolic outcomes than their male counterparts. SG females had improved weight loss maintenance, preservation of fat-free mass (FFM), higher total energy expenditure (TEE), normal locomotor activity, and reduced plasma insulin and white adipose tissue (WAT) inflammatory markers. SH-IF females also had lower plasma insulin and WAT inflammatory markers, and higher TEE than SH-IF males, despite their lower FFM. In addition, SH-IF females had higher iBAT sympathetic nerve density than SG and SH-AL females, whereas there were no differences among males. Notably, SH-IF mice of both sexes had the most improved glucose tolerance, highlighting the benefits of fasting, irrespective of weight loss. Results from this study demonstrate that in middle-aged obese mice, female sex is associated with better metabolic outcomes after SG or IF with calorie restriction. Clinical studies are needed to determine if sex differences should guide the choice of obesity therapies.NEW & NOTEWORTHY SG or IF with calorie restriction produces better metabolic outcomes in females than in males. IF with calorie restriction prevents metabolic adaptation, even in the face of fat-free mass loss. IF with calorie restriction in females only, is associated with increased iBAT sympathetic innervation, which possibly mitigates reductions in energy expenditure secondary to fat-free mass loss. Lastly, IF leads to better glucose homeostasis than SG, irrespective of sex.

Response to immune checkpoint blockade improved in pre-clinical model of breast cancer after bariatric surgery

Bariatric surgery is a sustainable weight loss approach, including vertical sleeve gastrectomy (VSG). Obesity exacerbates tumor growth, while diet-induced weight loss impairs progression. It remains unknown how bariatric surgery-induced weight loss impacts cancer progression or alters response to therapy. Using a pre-clinical model of obesity followed by VSG or diet-induced weight loss, breast cancer progression and immune checkpoint blockade therapy were investigated. Weight loss by VSG or weight-matched dietary intervention before tumor engraftment protected against obesity-exacerbated tumor progression. However, VSG was not as effective as diet in reducing tumor burden despite achieving similar weight and adiposity loss. Leptin did not associate with changes in tumor burden; however, circulating IL-6 was elevated in VSG mice. Uniquely, VSG tumors displayed elevated inflammation and immune checkpoint ligand PD-L1+ myeloid and non-immune cells. VSG tumors also had reduced T lymphocytes and markers of cytolysis, suggesting an ineffective anti-tumor microenvironment which prompted investigation of immune checkpoint blockade. While obese mice were resistant to immune checkpoint blockade, anti-PD-L1 potently impaired tumor progression after VSG through improved anti-tumor immunity. Thus, in formerly obese mice, surgical weight loss followed by immunotherapy reduced breast cancer burden. Finally, we compared transcriptomic changes in adipose tissue after bariatric surgery from patients and mouse models. A conserved bariatric surgery-associated weight loss signature (BSAS) was identified which significantly associated with decreased tumor volume. Findings demonstrate conserved impacts of obesity and bariatric surgery-induced weight loss pathways associated with breast cancer progression.

As the number of people classified as obese rises globally, so do obesity-related health risks. Studies show that people diagnosed with obesity have inflammation that contributes to tumor growth and their immune system is worse at detecting cancer cells. But weight loss is not currently used as a strategy for preventing or treating cancer.

Surgical procedures for weight loss, also known as ‘bariatric surgeries’, are becoming increasingly popular. Recent studies have shown that individuals who lose weight after these treatments have a reduced risk of developing tumors. But how bariatric surgery directly impacts cancer progression has not been well studied: does it slow tumor growth or boost the anti-tumor immune response?

To answer these questions, Sipe et al. compared breast tumor growth in groups of laboratory mice that were obese due to being fed a high fat diet. The first group of mice lost weight after undergoing a bariatric surgery in which part of their stomach was removed. The second lost the same amount of weight but after receiving a restricted diet, and the third underwent a fake surgery and did not lose any weight. The experiments found that surgical weight loss cuts breast cancer tumor growth in half compared with obese mice. But mice who lost the same amount of weight through dietary restrictions had even less tumor growth than surgically treated mice.

The surgically treated mice who lost weight had more inflammation than mice in the two other groups, and had increased amounts of proteins and cells that block the immune response to tumors. Giving the surgically treated mice a drug that enhances the immune system’s ability to detect and destroy cancer cells reduced inflammation and helped shrink the mice’s tumors. Finally, Sipe et al. identified 54 genes which were turned on or off after bariatric surgery in both mice and humans, 11 of which were linked with tumor size.

These findings provide crucial new information about how bariatric surgery can impact cancer progression. Future studies could potentially use the conserved genes identified by Sipe et al. to develop new ways to stimulate the anti-cancer benefits of weight loss without surgery.

Antiobesity, hepatoprotective and anti-hyperglycemic effects of a pharmaceutical formulation containing Cecropia pachystachya Trécul in mice fed with a hypercaloric diet

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of Cecropia pachystachya Trécul (Urticaceae), known as embaúba, are used as hypoglycemic and for weight reduction in Brazilian traditional medicine.

AIM OF THE STUDY

This study investigated the effects of a pharmaceutical formulation (ECP20) containing C. pachystachya extract on some metabolic alterations caused by a hypercaloric diet in mice.

MATERIAL AND METHODS

Mice were randomly fed with a standard or hypercaloric diet and orally treated with ECP20 or vehicle for 13 weeks. Subsequently, adiposity, glucose intolerance, and the presence of nonalcoholic fatty liver disease were assessed. Adipose tissue and liver were collected after euthanasia and frozen at -80 °C for histological and antioxidant analyzes. The effect of ECP20 on the differentiation of 3T3-L1 pre-adipocytes was also investigated.

RESULTS

Animals treated with ECP20 showed less weight gain, reduced glycemia, glucose tolerance restored, and hepatoprotective effect. Also, ECP20 presented significant in vivo antioxidant activity. Treatment of 3T3-L1 preadipocytes with ECP20 did not inhibit cellular differencing.

CONCLUSIONS

Therefore, ECP20 presented promising effects in the control of obesity and related disorders. Considering that glucose intolerance and hyperglycemia are strong evidence for the development of type 2 diabetes, the findings corroborated the traditional use of C. pachystachya to treat this disease. The chlorogenic acid and the flavonoids orientin and iso-orientin, present in the extract, might be involved in the activities found.

Effect of lactate administration on mouse skeletal muscle under calorie restriction

Calorie restriction (CR) involves a reductions of calorie intake without altering the nutritional balance, and has many beneficial effects, such as improving oxidative metabolism and extending lifespan. However, CR decreases in skeletal muscle mass and fat mass in correlation with the reduction in food intake. Lactate is known to have potential as a signaling molecule rather than a metabolite during exercise. In this study, we examined the effects of the combination of caloric restriction and lactate administration on skeletal muscle adaptation in order to elucidate a novel role of lactate. We first demonstrated that daily lactate administration (equivalent to 1 g/kg of body weight) for 2 weeks suppressed CR-induced muscle atrophy by activating mammalian/mechanistic target of rapamycin (mTOR) signaling, a muscle protein synthesis pathway, and inhibited autophagy-induced muscle degradation. Next, we found that lactate administration under calorie restriction enhanced mitochondrial enzyme activity (citrate synthase and succinate dehydrogenase) and the expression of oxidative phosphorylation (OXPHOS) protein expression. Our results suggest that lactate administration under caloric restriction not only suppresses muscle atrophy but also improves mitochondrial function.

Perirenal Adipose Tissue Inflammation: Novel Insights Linking Metabolic Dysfunction to Renal Diseases

A healthy adipose tissue (AT) is indispensable to human wellbeing. Among other roles, it contributes to energy homeostasis and provides insulation for internal organs. Adipocytes were previously thought to be a passive store of excess calories, however this view evolved to include an endocrine role. Adipose tissue was shown to synthesize and secrete adipokines that are pertinent to glucose and lipid homeostasis, as well as inflammation. Importantly, the obesity-induced adipose tissue expansion stimulates a plethora of signals capable of triggering an inflammatory response. These inflammatory manifestations of obese AT have been linked to insulin resistance, metabolic syndrome, and type 2 diabetes, and proposed to evoke obesity-induced comorbidities including cardiovascular diseases (CVDs). A growing body of evidence suggests that metabolic disorders, characterized by AT inflammation and accumulation around organs may eventually induce organ dysfunction through a direct local mechanism. Interestingly, perirenal adipose tissue (PRAT), surrounding the kidney, influences renal function and metabolism. In this regard, PRAT emerged as an independent risk factor for chronic kidney disease (CKD) and is even correlated with CVD. Here, we review the available evidence on the impact of PRAT alteration in different metabolic states on the renal and cardiovascular function. We present a broad overview of novel insights linking cardiovascular derangements and CKD with a focus on metabolic disorders affecting PRAT. We also argue that the confluence among these pathways may open several perspectives for future pharmacological therapies against CKD and CVD possibly by modulating PRAT immunometabolism.

Age-Dependent Changes of Adipokine and Cytokine Secretion From Rat Adipose Tissue by Endogenous and Exogenous Toll-Like Receptor Agonists

White adipose tissue but recently also brown adipose tissue have emerged as endocrine organs. Age-associated obesity is accompanied by prolonged and elevated lipopolysaccharide (LPS)-induced sickness symptoms and increased cytokine and adipokine levels in the circulation partially originating from adipose tissue. In the present study, ex vivo fat explants were used to investigate how the exogenous pathogen-associated molecular pattern (PAMP) LPS or the endogenous danger-associated molecular patterns (DAMPs) high mobility group box-1 protein (HMGB1) and biglycan modulate the release of cytokines and adipokines/batokines and, thus, could influence systemic and/or local inflammation. The response of adipose tissue (epididymal, retroperitoneal, subcutaneous, and brown) was compared between young lean and old obese rats (2 vs. 24 months old). LPS induced a strong interleukin (IL)-6 and tumor necrosis factor (TNF) alpha release into the supernatant of all adipose tissue types investigated. HMGB1 (subcutaneous) and biglycan (retroperitoneal) led to an increased release of IL-6 and TNFalpha (HMGB1) and decreased visfatin and adiponectin (biglycan) secretion from epididymal adipose tissue (young rats). Visfatin was also decreased by HMGB1 in retroperitoneal adipose tissue of old rats. We found significantly higher leptin (all fat pads) and adiponectin (subcutaneous) levels in supernatants of adipose tissue from old compared to young rats, whereas visfatin secretion showed the opposite. The expression of the biglycan receptor Toll-like receptor (TLR) 2 as well as the LPS and HMGB1 receptors TLR4 and receptor for advanced glycation end products (RAGE) were reduced with age (TLR4/RAGE) and by stimulation with their ligands (subcutaneous). Overall, we revealed that adipokines/adipose-tissue released cytokines show some modulation of their release caused by mediators of septic (batokines) and sterile inflammation with potential implication for acute and chronic disease. Moreover, aging may increase or decrease the release of fat-derived mediators. These data show that DAMPS and LPS locally modulate cytokine secretion while only DAMPS but not LPS can locally alter adipokine secretion during inflammation.

Obesity-induced sympathoexcitation is associated with Nrf2 dysfunction in the rostral ventrolateral medulla

Increases in sympathetic nerve activity (SNA) have been implicated in obesity-induced risk for cardiovascular diseases, especially hypertension. Previous studies indicate that oxidative stress in the rostral ventrolateral medulla (RVLM), a key brain stem region that regulates sympathetic outflow to peripheral tissues, plays a pathogenic role in obesity-mediated sympathoexcitation. However, the molecular mechanisms underlying this phenomenon are not clear. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that regulates the expression of antioxidant and anti-inflammatory genes and confers cytoprotection against oxidative stress. The present study was designed to investigate whether Nrf2 dysfunction was associated with obesity-induced oxidative stress in the RVLM and sympathoexcitation. C57BL/6J mice were fed with chow or a high-fat diet (HFD) for 16 wk. Blood pressure parameters were assessed by radiotelemeters in conscious freely moving mice. SNA was measured by heart rate variability analysis and also through assessment of depressor response to ganglionic blockade. The RVLM was microdissected for gene expression and protein analysis (Western blot analysis and activity assay) related to Nrf2 signaling. Our results showed that HFD-induced obesity resulted in significant increases in SNA, although we only observed a mild increase in mean arterial pressure. Obesity-induced oxidative stress in the RVLM was associated with impaired Nrf2 signaling marked by decreased Nrf2 activity, downregulation of Nrf2 mRNA, its target genes [NAD(P)H quinone dehyrogenase 1 (Nqo1) and superoxide dismutase 2 (Sod2)], and inflammation. Our findings suggest that obesity results in Nrf2 dysfunction, which likely causes maladaptation to oxidative stress and inflammation in the RVLM. These mechanisms could potentially contribute to obesity-induced sympathoexcitation.

Molecular pathways linking adipose innervation to insulin action in obesity and diabetes mellitus

Adipose tissue comprises adipocytes and many other cell types that engage in dynamic crosstalk in a highly innervated and vascularized tissue matrix. Although adipose tissue has been studied for decades, it has been appreciated only in the past 5 years that extensive arborization of nerve fibres has a dominant role in regulating the function of adipose tissue. This Review summarizes the latest literature, which suggests that adipocytes signal to local sensory nerve fibres in response to perturbations in lipolysis and lipogenesis. Such adipocyte signalling to the central nervous system causes sympathetic output to distant adipose depots and potentially other metabolic tissues to regulate systemic glucose homeostasis. Paracrine factors identified in the past few years that mediate such adipocyte-neuron crosstalk are also reviewed. Similarly, immune cells and endothelial cells within adipose tissue communicate with local nerve fibres to modulate neurotransmitter tone, blood flow, adipocyte differentiation and energy expenditure, including adipose browning to produce heat. This understudied field of neurometabolism related to adipose tissue biology has great potential to reveal new mechanistic insights and potential therapeutic strategies for obesity and type 2 diabetes mellitus.

Impact of the Autonomic Nervous System on the Skeleton

It is from the discovery of leptin and the central nervous system as a regulator of bone remodeling that the presence of autonomic nerves within the skeleton transitioned from a mere histological observation to the mechanism whereby neurons of the central nervous system communicate with cells of the bone microenvironment and regulate bone homeostasis. This shift in paradigm sparked new preclinical and clinical investigations aimed at defining the contribution of sympathetic, parasympathetic, and sensory nerves to the process of bone development, bone mass accrual, bone remodeling, and cancer metastasis. The aim of this article is to review the data that led to the current understanding of the interactions between the autonomic and skeletal systems and to present a critical appraisal of the literature, bringing forth a schema that can put into physiological and clinical context the main genetic and pharmacological observations pointing to the existence of an autonomic control of skeletal homeostasis. The different types of nerves found in the skeleton, their functional interactions with bone cells, their impact on bone development, bone mass accrual and remodeling, and the possible clinical or pathophysiological relevance of these findings are discussed.

Lorcaserin and metabolic disease: weight-loss dependent and independent effects

OBJECTIVE

Weight management pharmacotherapies can improve metabolic diseases through weight-dependent and weight-independent effects. Lorcaserin is a selective 5-hydroxytryptamine 2C receptor agonist. The objective of this analysis is to quantify the relative contribution of weight loss to the treatment effects of lorcaserin 10 mg twice a day on key metabolic parameters.

METHODS

This retrospective analysis evaluated 6,897 patients with overweight or obesity (with or without diabetes mellitus) across three randomized, placebo-controlled, double-blind, 52-week clinical trials that evaluated lorcaserin 10 mg twice daily (BID; NCT00395135, NCT00603902, and NCT00603291); 509 patients from only one of the studies had type 2 diabetes mellitus. A mediation analysis was applied to help rank the relative contribution of weight loss to metabolic study outcomes.

RESULTS

According to this mediation analysis, lorcaserin 10 mg BID improved a spectrum of adiposopathic metabolic abnormalities with varying contributions attributable to weight loss. Improvements in waist circumference and blood pressure were almost exclusively attributable to weight loss. Less than 50% of the improvement in glucose parameters (fasting blood glucose and haemoglobin A1c) were attributable to weight loss.

CONCLUSIONS

Across Phase III clinical trials, lorcaserin 10 mg BID improved multiple cardiometabolic parameters through both weight-loss dependent and independent mechanisms.

Factors Associated with Visceral Fat Loss in Response to a Multifaceted Weight Loss Intervention

Background

Visceral adipose tissue is more metabolically active than other fat depots and is more closely associated with obesity-related diseases, such as cardiovascular disease and type 2 diabetes, than indicators of obesity, such as body mass index. Across various strategies to promote weight loss, including energy-reduced diet and exercise, variable effects on VAT compared to loss of total body fat have been reported.

Methods

To examine the effect of a behavioral weight loss intervention using portion-controlled prepackaged entrées on VAT, we examined data and measurements from overweight/obese men and women (N=183) who were assigned to a weight loss intervention and prescribed a reduced-energy diet with either portion-controlled prepackaged entrées or self-selected meals in a randomized clinical trial. VAT was estimated with dual-energy X-ray absorptiometry at baseline and study end (12 weeks).

Results

VAT loss was greater for the prepackaged entrees group (p=0.02), with an average loss of 29% compared to an average loss of 19% among participants consuming self-selected meals. VAT (mean [SEM]) was 1651 (71) g and 1546 (157) g at baseline and 1234 (59) g and 1278 (118) g at study end in the prepackaged entrees and self-selected meal groups, respectively. Greater VAT loss was associated with higher baseline weight and VAT, and greater weight loss, but not associated with age or physical activity.

Conclusion

Prescribing portion-controlled prepackaged entrees in a behavioral weight loss intervention promotes a reduction in VAT, which should promote improved metabolic profile and reduced cardiovascular disease risk.