Targeting Energy Expenditure-Drugs for Obesity Treatment

The dairy-derived peptide Miltin exerts anti-obesity effects by increasing adipocyte thermogenesis

Growing research has highlighted that the consumption of dairy products improves the metabolic health in obese individuals by functioning as regulatory modulators. However, the molecular basis of this effect remains largely unknown. Herein, we report a dairy-derived peptide, which we named Miltin, that activates the thermogenesis of brown adipocytes and increases white adipocyte browning. Previously, Miltin was merely identified for its antioxidant capacity, although it is commonly present in different dairy products. In this study, we revealed the effect of Miltin in modulating adipose thermogenesis and further explored its potential in treating obesity through in vivo and in vitro strategies. The administration of Miltin in mice fed with a high-fat diet resulted in enhanced thermogenesis, improved glucose homeostasis, and reduced body mass and lipid accumulation, indicating the anti-obesity effect of Miltin. Genomic analysis revealed that Miltin modulates thermogenesis by inducing the activation of the MAPK signaling pathway by preferentially interacting with GADD45γ to promote its stability. Together, our findings indicate that Miltin's role in initiating the thermogenesis of adipocytes makes it a potential anti-obesity therapy for future development.

A Synergistic Botanical Composition Increases Resting Energy Expenditure and Reduces Adiposity in High-Fat Diet-Fed Rats

OBJECTIVE

An imbalance between dietary energy intake and energy expenditure may result in body fat gain or obesity. Increasing resting energy expenditure (REE) is an attractive strategy for managing body fat gain. The objective of the current study was to generate proof-of-concept data on a synergistic composition (LN19183) of Citrus aurantifolia fruit rind (CA) and Theobroma cacao seed (TC) extracts to increase REE and reduce body fat gain in a high-fat diet (HFD)-fed rats.

METHOD

In in vitro cell-based experiments, CA, TC, or LN19183 were tested for fibroblast growth factor 21 (FGF-21) production from 3T3-L1 mouse adipocytes. Uncoupling protein 1 (UCP-1) and beta3-adrenergic receptor (β3-AR) protein expressions in LN19183-treated 3T3-L1 lysates were also tested. The 56-day in vivo study in male Sprague Dawley (SD) rats (age: 12-14 weeks; body weight [b.w.]: 115-197 g) contained 2 phases of 28 days each of induction and supplementation. Seven rats received a regular rodent diet (RD) over 56 days. In the induction phase, 21 rats received HFD; in the supplementation phase, the obese rats (n = 7) received either HFD alone or in concurrence with a daily oral dose of either 100 or 250 mg/kg b.w. of LN19183 for 28 days.

RESULTS

In 3T3-L1 adipocytes, LN19183 synergistically increased FGF-21 production and dose-dependently increased β3-AR and UCP-1 protein expression. In HFD-fed rats, both doses of LN19183 supplementation significantly (p < 0.05) decreased the body weight gain, total fat mass, and liver weight and increased (p < 0.05) REE. High-dose LN19183 also significantly (p < 0.05) increased fat oxidation and UCP-1 protein expression in white fat tissue and reduced liver triglyceride (TG) level. LN19183-supplemented groups substantially reduced serum TG and glucose levels compared to the HFD rats.

CONCLUSIONS

LN19183 reduces body fat mass and weight gain via increased REE and fat oxidation in HFD-fed obese rats.

Antiobesity effect of Kaempferia parviflora accompanied by inhibition of lipogenesis and stimulation of lipolysis

Background

Obesity occurs when energy intake is excessive compared to energy expenditure, resulting in the excessive storage of triglyceride in adipose tissue.

Objective

The present study aimed to investigate the antiobesity effects of Kaempferia parviflora extracts (PF) in high-fat diet (HFD)-induced obese mice and 3T3-L1 adipocytes to demonstrate the lipid mechanisms underlying these effects.

Design

Mice were fed with a normal diet (AIN93G normal diet), HFD (60% HFD), Met (HFD containing metformin 250 mg/kg b.w.), PF50 (HFD containing PF 50 mg/kg b.w.), and PF100 (HFD containing PF 100 mg/kg b.w.) for 12 weeks.

Results

Body weight gain, adipose tissue weight, adipose tissue mass, and size of adipocytes were significantly decreased by PF supplementation in HFD-fed mice. Moreover, PF supplementation suppressed the adipogenesis and lipogenesis pathways and activated the lipolysis and thermogenesis pathways in the adipose tissues of HFD-fed mice.

Conclusions

PF treatment during the differentiation of 3T3-L1 cells suppressed adipogenesis and lipogenesis and PF treatment after differentiation activated lipolysis and thermogenesis. Thus, we suggest that PF is effective for weight loss by directly affecting the lipid metabolism of adipocytes.

Green Tea and Java Pepper Mixture Prevents Obesity by Increasing Energy Expenditure and Modulating Hepatic AMPK/MicroRNA-34a/370 Pathway in High-Fat Diet-Fed Rats

This study was performed to evaluate the anti-obesity effects of green tea and java pepper mixture (GJ) on energy expenditure and understand the regulatory mechanisms of AMP-activated protein kinase (AMPK), microRNA (miR)-34a, and miR-370 pathways in the liver. Sprague-Dawley rats were divided into four groups depending on the following diets given for 14 weeks: normal chow diet (NR), 45% high-fat diet (HF), HF + 0.1% GJ (GJL), and HF + 0.2% GJ (GJH). The results revealed that GJ supplementation reduced body weight and hepatic fat accumulation, improved serum lipids, and increased energy expenditure. In the GJ-supplemented groups, the mRNA levels of genes related to fatty acid syntheses, such as a cluster of differentiation 36 (CD36), sterol regulatory element binding protein-1c (SREBP-1c), fatty acid synthase (FAS), and stearoyl-CoA desaturase 1 (SCD1) were downregulated, and mRNA levels of peroxisome proliferator-activated receptor alpha (PPARα), carnitine/palmitoyl-transferase 1 (CPT1), and uncoupling protein 2 (UCP2), which participate in fatty acid oxidation, were upregulated in the liver. GJ increased the AMPK activity and decreased the miR-34a and miR-370 expression. Therefore, GJ prevented obesity by increasing energy expenditure and regulating hepatic fatty acid synthesis and oxidation, suggesting that GJ is partially regulated through AMPK, miR-34a, and miR-370 pathways in the liver.

Glucagon and energy expenditure; Revisiting amino acid metabolism and implications for weight loss therapy

Glucagon receptor (GCGR)-targeted multi-agonists are being developed for the treatment of obesity and metabolic disease. GCGR activity is utilised for its favourable weight loss and metabolic properties, including increased energy expenditure (EE) and hepatic lipid metabolism. GLP1R and GIPR activities are increasingly present in a multi-agonist strategy. Due to the compound effect of increased satiety, reduced food intake and increased energy expenditure, the striking weight loss effects of these multi-agonists has been demonstrated in pre-clinical models of obesity. The precise contribution and mechanism of GCGR activity to enhanced energy expenditure and weight loss in both rodents and humans is not fully understood. In this review, our understanding of glucagon-mediated EE is explored, and an amino acid-centric paradigm contributing to this phenomenon is presented. The current progress of GCGR-targeted multi-agonists in development is also highlighted with a focus on the implications of glucagon-stimulated hypoaminoacidemia.

Remodeling of white adipose tissue microenvironment against obesity by phytochemicals

Obesity is a kind of chronic disease due to a long-term imbalance between energy intake and expenditure. In recent years, the number of obese people around the world has soared, and obesity problem should not be underestimated. Obesity is characterized by changes in the adipose microenvironment, mainly manifested as hypertrophy, chronic inflammatory status, hypoxia, and fibrosis, thus contributing to the pathological changes of other tissues. A plethora of phytochemicals have been found to improve adipose microenvironment, thus prevent and resist obesity, providing a new research direction for the treatment of obesity and related diseases. This paper discusses remodeling of the adipose tissue microenvironment as a therapeutic avenue and reviews the progress of phytochemicals in fighting obesity by improving the adipose microenvironment.

BI 456906: Discovery and preclinical pharmacology of a novel GCGR/GLP-1R dual agonist with robust anti-obesity efficacy

OBJECTIVE

Obesity and its associated comorbidities represent a global health challenge with a need for well-tolerated, effective, and mechanistically diverse pharmaceutical interventions. Oxyntomodulin is a gut peptide that activates the glucagon receptor (GCGR) and glucagon-like peptide-1 receptor (GLP-1R) and reduces bodyweight by increasing energy expenditure and reducing energy intake in humans. Here we describe the pharmacological profile of the novel glucagon receptor (GCGR)/GLP-1 receptor (GLP-1R) dual agonist BI 456906.

METHODS

BI 456906 was characterized using cell-based in vitro assays to determine functional agonism. In vivo pharmacological studies were performed using acute and subchronic dosing regimens to demonstrate target engagement for the GCGR and GLP-1R, and weight lowering efficacy.

RESULTS

BI 456906 is a potent, acylated peptide containing a C18 fatty acid as a half-life extending principle to support once-weekly dosing in humans. Pharmacological doses of BI 456906 provided greater bodyweight reductions in mice compared with maximally effective doses of the GLP-1R agonist semaglutide. BI 456906's superior efficacy is the consequence of increased energy expenditure and reduced food intake. Engagement of both receptors in vivo was demonstrated via glucose tolerance, food intake, and gastric emptying tests for the GLP-1R, and liver nicotinamide N-methyltransferase mRNA expression and circulating biomarkers (amino acids, fibroblast growth factor-21) for the GCGR. The dual activity of BI 456906 at the GLP-1R and GCGR was supported using GLP-1R knockout and transgenic reporter mice, and an ex vivo bioactivity assay.

CONCLUSIONS

BI 456906 is a potent GCGR/GLP-1R dual agonist with robust anti-obesity efficacy achieved by increasing energy expenditure and decreasing food intake.

Dose-Dependent Effect of Melatonin on BAT Thermogenesis in Zücker Diabetic Fatty Rat: Future Clinical Implications for Obesity

Experimental data have revealed that melatonin at high doses reduced obesity and improved metabolic outcomes in experimental models of obesity, mainly by enhancing brown adipose tissue (BAT) thermogenesis. A potential dose-response relationship has yet to be performed to translate these promising findings into potential clinical therapy. This study aimed to assess the effects of different doses of melatonin on interscapular BAT (iBAT) thermogenic capacity in Zücker diabetic fatty (ZDF) rats. At 6 wk of age, male ZDF rats were divided into four groups (n = 4 per group): control and those treated with different doses of melatonin (0.1, 1, and 10 mg/kg of body weight) in their drinking water for 6 wk. Body weight (BW) was significantly decreased at doses of 1 and 10 mg/kg of melatonin, but not at 0.1 mg/kg compared with the control, with a similar rate of BW decrease being reached at the dose of 1 mg/kg (by ~11%) and 10 mg/kg (by ~12%). This effect was associated with a dose-dependent increase in the thermal response to the baseline condition or acute cold challenge in the interscapular area measurable by infrared thermography, with the highest thermal response being recorded at the 10 mg/kg dose. Upon histology, melatonin treatment markedly restored the typical brownish appearance of the tissue and promoted a shift in size distribution toward smaller adipocytes in a dose-dependent fashion, with the most pronounced brownish phenotype being observed at 10 mg/kg of melatonin. As a hallmark of thermogenesis, the protein level of uncoupled protein 1 (UCP1) from immunofluorescence and Western blot analysis increased significantly and dose-dependently at all three doses of melatonin, reaching the highest level at the dose of 10 mg/kg. Likewise, all three doses of melatonin modulated iBAT mitochondrial dynamics by increasing protein expression of the optic atrophy protein type 1 (OPA1) fusion marker and decreasing that of the dynamin-related protein1 (DRP1) fission marker, again dose-dependently, with the highest and lowest expression levels, respectively, being reached at the 10 mg/kg dose. These findings highlight for the first time the relevance of the dose-dependency of melatonin toward BW control and BAT thermogenic activation, which may have potential therapeutic implications for the treatment of obesity. To clinically apply the potential therapeutic of melatonin for obesity, we consider that the effective animal doses that should be extrapolated to obese individuals may be within the dose range of 1 to 10 mg/kg.

Colchicine stimulates browning via antagonism of GABA receptor B and agonism of β3-adrenergic receptor in 3T3-L1 white adipocytes

Colchicine has been used for therapeutic purposes and has attracted considerable attention because of its association with tubulin and the inhibition of small tubular polymerization. Although several studies have examined the possible preventive role of colchicine in metabolic diseases, its role in adipocytes is largely unknown. This study examined the novel functional role of colchicine in adipocytes demonstrating that colchicine stimulates browning in cultured white adipocytes. Colchicine stimulates browning by increasing the brown- and beige fat-specific markers in 3T3-L1 white adipocytes. Interestingly, colchicine decreased the expression of the main lipolytic proteins (ATGL, p-HSL) while it activated Ces3, suggesting a possibility for supplying essential fatty acids for inducing thermogenesis. Molecular docking analysis showed that colchicine has a strong affinity against GABA-BR and β3-AR, and its binding activity with GABA-BR (-26.52 kJ/mol) was stronger than β3-AR (-20.71 kJ/mol). Mechanistic studies were conducted by treating the cells separately with agonists and antagonists of GABA-BR and β3-AR to understand the molecular mechanism underlying the browning effect of colchicine. The results showed that colchicine stimulates browning via the antagonism of GABA-BR and the agonism of β3-AR in 3T3-L1 white adipocytes. The colchicine-mediated activation of β3-AR stimulated the PKA/p38 MAPK signaling pathway, where consequently ATF2 acted as a positive regulator, but AFT4 was a negative regulator for the induction of browning.

Guanabenz-an old drug with a potential to decrease obesity

The aim of this study was to determine, in the diet-induced obesity model in rats, the potential of Guanabenz to reduce body weight and ameliorate some metabolic disturbances. Obesity was induced in rats by a high-fat diet. After 10 weeks, rats were treated intraperitoneally with Guanabenz at the two doses: 2 or 5 mg/kg b.w./day, once daily for 25 days. The spontaneous activity of rats was measured for 24 h on the 1st and 24th day of the Guanabenz treatment with a special radio-frequency identification system. Gastric emptying was measured in intragastric phenol red-treated mice by measuring the color of the stomach homogenate 30 min after phenol red administration. Intraperitoneal administration of Guanabenz for 25 days to obese rats resulted in a significant decrease in body weight compared to the baseline values (about 11% at a dose of 5 mg/kg). Both body weight and the amount of adipose tissue in the groups receiving Guanabenz decreased to the levels observed in the control rats fed only standard feed. The anorectic effect occurred in parallel with a reduction in plasma triglyceride levels. We also confirmed the beneficial effect of Guanabenz on plasma glucose level. The present study demonstrates that the administration of Guanabenz strongly inhibits gastric emptying (about 80% at a dose of 5 mg/kg). Guanabenz can successfully and simultaneously attenuate all the disorders and risk factors of metabolic syndrome: hypertension, hyperglycemia, obesity, and dyslipidemia. However, the exact cellular mechanisms of its action require further research.

Melanocortin-4 receptor complexity in energy homeostasis,obesity and drug development strategies

The melanocortin-4 receptor (MC4R) has been critically investigated for the past two decades, and novel findings regarding MC4R signalling and its potential exploitation in weight loss therapy have lately been emphasized. An association between MC4R and obesity is well established, with disease-causing mutations affecting 1% to 6% of obese patients. More than 200 MC4R variants have been reported, although conflicting results as to their effects have been found in different cohorts. Most notably, some MC4R gain-of-function variants seem to rescue obesity and related complications via specific pathways such as beta-arrestin (ß-arrestin) recruitment. Broadly speaking, however, dysfunctional MC4R dysregulates satiety and induces hyperphagia. The picture at the mechanistic level is complicated as, in addition to the canonical G stimulatory pathway, the ß-arrestin signalling pathway and ions (particularly calcium) seem to interact with MC4R signalling to contribute to or alleviate obesity pathogenesis. Thus, the overall complexity of the MC4R signalling spectra has broadened considerably, indicating there is great potential for the development of new drugs to manage obesity and its related complications. Alpha-melanocyte-stimulating hormone is the major endogenous MC4R agonist, but structure-based ligand discovery studies have identified possible superior and selective agonists that can improve MC4R function. However, some of these agonists characterized in vitro and in vivo confer adverse effects in patients, as demonstrated in clinical trials. In this review, we provide a comprehensive insight into the genetics, function and regulation of MC4R and its contribution to obesity. We also outline new approaches in drug development and emerging drug candidates to treat obesity.

Mitophagy Mediates the Beige to White Transition of Human Primary Subcutaneous Adipocytes Ex Vivo

Brown and beige adipocytes have multilocular lipid droplets, express uncoupling protein (UCP) 1, and promote energy expenditure. In rodents, when the stimulus of browning subsides, parkin-dependent mitophagy is activated and dormant beige adipocytes persist. In humans, however, the molecular events during the beige to white transition have not been studied in detail. In this study, human primary subcutaneous abdominal preadipocytes were differentiated to beige for 14 days, then either the beige culture conditions were applied for an additional 14 days or it was replaced by a white medium. Control white adipocytes were differentiated by their specific cocktail for 28 days. Peroxisome proliferator-activated receptor γ-driven beige differentiation resulted in increased mitochondrial biogenesis, UCP1 expression, fragmentation, and respiration as compared to white. Morphology, UCP1 content, mitochondrial fragmentation, and basal respiration of the adipocytes that underwent transition, along with the induction of mitophagy, were similar to control white adipocytes. However, white converted beige adipocytes had a stronger responsiveness to dibutyril-cAMP, which mimics adrenergic stimulus, than the control white ones. Gene expression patterns showed that the removal of mitochondria in transitioning adipocytes may involve both parkin-dependent and -independent pathways. Preventing the entry of beige adipocytes into white transition can be a feasible way to maintain elevated thermogenesis and energy expenditure.

Treatment of Acquired Hypothalamic Obesity: Now and the Future

The hypothalamus is the centre of neuroendocrine regulation of energy homeostasis and appetite. Maldevelopment of, or damage to, the key hypothalamic nuclei disrupts the coordinated balance between energy intake and expenditure leading, to rapid and excessive weight gain. Hypothalamic obesity is compounded by a disruption of the hypothalamic-pituitary axis, sleep disruption, visual compromise, and neurological and vascular sequalae. Amongst suprasellar tumors, craniopharyngioma is the most common cause of acquired hypothalamic obesity, either directly or following surgical or radiotherapeutic intervention. At present, therapy is limited to strategies to manage obesity but with a modest and variable impact. Current approaches include optimizing pituitary hormone replacement, calorie restriction, increased energy expenditure through physical activity, behavioral interventions, pharmacotherapy and bariatric surgery. Current pharmacotherapeutic approaches include stimulants that increase energy consumption, anti-diabetic agents, hypothalamic-pituitary substitution therapy, octreotide, and methionine aminopeptidase 2 (MetAP2) inhibitors. Some pharmacological studies of hypothalamic obesity report weight loss or stabilization but reported intervention periods are short, and others report no effect. The impact of bariatric surgery on weight loss in hypothalamic obesity again is variable. Novel or combined approaches to manage hypothalamic obesity are thus required to achieve credible and sustained weight loss. Identifying etiological factors contributing hypothalamic obesity may lead to multi-faceted interventions targeting hyperphagia, insulin resistance, decreased energy expenditure, sleep disturbance, hypopituitarism and psychosocial morbidity. Placebo-controlled trials using current single, or combination therapies are required to determine the impact of therapeutic agents. A well-defined approach to defining the location of hypothalamic damage may support the use of future targeted therapies. Intranasal oxytocin is currently being investigated as an anorexogenic agent. Novel agents including those targeting pro-opimelanocortin-C and AgRP/NPY expressing neurons and the MC4 receptor may result in better outcomes. This article discusses the current challenges in the management of hypothalamic obesity in children and young people and future therapeutic approaches to increasing weight loss and quality of life in these patients.

BMP7 Increases UCP1-Dependent and Independent Thermogenesis with a Unique Gene Expression Program in Human Neck Area Derived Adipocytes

White adipocytes contribute to energy storage, accumulating lipid droplets, whereas brown and beige adipocytes mainly function in dissipating energy as heat primarily via the action of uncoupling protein 1 (UCP1). Bone morphogenic protein 7 (BMP7) was shown to drive brown adipocyte differentiation in murine interscapular adipose tissue. Here, we performed global RNA-sequencing and functional assays on adipocytes obtained from subcutaneous (SC) and deep-neck (DN) depots of human neck and differentiated with or without BMP7. We found that BMP7 did not influence differentiation but upregulated browning markers, including UCP1 mRNA and protein in SC and DN derived adipocytes. BMP7 also enhanced mitochondrial DNA content, levels of oxidative phosphorylation complex subunits, along with PGC1α and p-CREB upregulation, and fragmentation of mitochondria. Furthermore, both UCP1-dependent proton leak and UCP1-independent, creatine-driven substrate cycle coupled thermogenesis were augmented upon BMP7 addition. The gene expression analysis also shed light on the possible role of genes unrelated to thermogenesis thus far, including ACAN, CRYAB, and ID1, which were among the highest upregulated ones by BMP7 treatment in both types of adipocytes. Together, our study shows that BMP7 strongly upregulates thermogenesis in human neck area derived adipocytes, along with genes, which might have a supporting role in energy expenditure.