Revisiting adipose thermogenesis for delaying aging and age-related diseases: Opportunities and challenges

Regulatory effects of yam (Dioscorea opposita Thunb.) glycoprotein on energy metabolism in C2C12 and 3T3-L1 cells and on crosstalk between these two cells

ETHNOPHARMACOLOGICAL RELEVANCE

Controlling energy and regulating metabolism have been key strategies in the treatment of metabolic disorders such as obesity. Yam glycoprotein (Y-Gly) is a polysaccharide-protein complex extracted from Chinese yam that has beneficial effects on glucose and lipid metabolism. This study aimed to investigate the role of Y-Gly in regulating energy metabolism in C2C12 and 3T3-L1 cells.

MATERIALS AND METHODS

Y-Gly was subjected to extraction and chemo-profiling. Staining methods, assay kits, Western Blot and transcriptomics were mainly used to determine the role of Y-Gly. Additionally, the study sought to examine the impact of Y-Gly on white adipose browning in 3T3-L1 cells, employing a cell co-culture technique.

RESULTS

Y-Gly promoted myotube differentiation in C2C12 myoblasts, increased cellular glucose consumption, promoted ATP synthesis and mitochondrial biogenesis, and played an active role in energy expenditure and glycolipid metabolism related pathways such as AMPK and MAPK. The introduction of Y-Gly inhibited lipid accumulation after lipogenesis in 3T3-L1 cells, facilitated induction of white adipose browning related proteins such as PPARγ and UCP1 expression, and the effect was more significant after cell co-culture.

CONCLUSIONS

Y-Gly regulates glucose and lipid metabolism by activating the key proteins in the aforementioned pathways, and plays a role in energy metabolism regulation through crosstalk between muscle and adipose tissues. This suggests a possible role of Y-Gly in metabolism-related diseases.

Chronic β3-AR stimulation activates distinct thermogenic mechanisms in brown and white adipose tissue and improves systemic metabolism in aged mice

Adipose thermogenesis has been actively investigated as a therapeutic target for improving metabolic dysfunction in obesity. However, its applicability to middle-aged and older populations, which bear the highest obesity prevalence in the United States (approximately 40%), remains uncertain due to age-related decline in thermogenic responses. In this study, we investigated the effects of chronic thermogenic stimulation using the β3-adrenergic (AR) agonist CL316,243 (CL) on systemic metabolism and adipose function in aged (18-month-old) C57BL/6JN mice. Sustained β3-AR treatment resulted in reduced fat mass, increased energy expenditure, increased fatty acid oxidation and mitochondrial activity in adipose depots, improved glucose homeostasis, and a favorable adipokine profile. At the cellular level, CL treatment increased uncoupling protein 1 (UCP1)-dependent thermogenesis in brown adipose tissue (BAT). However, in white adipose tissue (WAT) depots, CL treatment increased glycerol and lipid de novo lipogenesis (DNL) and turnover suggesting the activation of the futile substrate cycle of lipolysis and reesterification in a UCP1-independent manner. Increased lipid turnover was also associated with the simultaneous upregulation of proteins involved in glycerol metabolism, fatty acid oxidation, and reesterification in WAT. Further, a dose-dependent impact of CL treatment on inflammation was observed, particularly in subcutaneous WAT, suggesting a potential mismatch between fatty acid supply and oxidation. These findings indicate that chronic β3-AR stimulation activates distinct cellular mechanisms that increase energy expenditure in BAT and WAT to improve systemic metabolism in aged mice. Considering that people lose BAT with aging, activation of futile lipid cycling in WAT presents a novel strategy for improving age-related metabolic dysfunction.

Glutathione peroxidase 3 is essential for countering senescence in adipose remodelling by maintaining mitochondrial homeostasis

Adipose tissue senescence is a precursor to organismal aging and understanding adipose remodelling contributes to discovering novel anti-aging targets. Glutathione peroxidase 3 (GPx3), a critical endogenous antioxidant enzyme, is diminished in the subcutaneous adipose tissue (sWAT) with white adipose expansion. Based on the active role of the antioxidant system in counteracting aging, we investigated the involvement of GPx3 in adipose senescence. We determined that knockdown of GPx3 in adipose tissue by adeno-associated viruses impaired mitochondrial function in mice, increased susceptibility to obesity, and exacerbated adipose tissue senescence. Impairment of GPx3 may cause mitochondrial dysfunction through inner mitochondrial membrane disruption. Adipose reshaping management (cold stimulation and intermittent diet) counteracted the aging of tissues, with an increase in GPx3 expression. Overall metabolic improvement induced by cold stimulation was partially attenuated when GPx3 was depleted. GPx3 may be involved in adipose browning by interacting with UCP1, and GPx3 may be a limiting factor for intracellular reactive oxygen species (ROS) accumulation during stem cell browning. Collectively, these findings emphasise the importance of restoring the imbalanced redox state in adipose tissue to counteract aging and that GPx3 may be a potential target for maintaining mitochondrial homeostasis and longevity.

Biomarker patterns and mechanistic insights into hypothermia from a postmortem metabolomics investigation

Postmortem metabolomics holds promise for identifying crucial biological markers relevant to death investigations and clinical scenarios. We aimed to assess its applicability in diagnosing hypothermia, a condition lacking definitive biomarkers. Our retrospective analysis involved 1095 postmortem femoral blood samples, including 150 hypothermia cases, 278 matched controls, and 667 randomly selected test cases, analyzed using UHPLC-QTOF mass spectrometry. The model demonstrated robustness with an R2 and Q2 value of 0.73 and 0.68, achieving 94% classification accuracy, 92% sensitivity, and 96% specificity. Discriminative metabolite patterns, including acylcarnitines, stress hormones, and NAD metabolites, along with identified pathways, suggest that metabolomics analysis can be helpful to diagnose fatal hypothermia. Exposure to cold seems to trigger a stress response in the body, increasing cortisol production to maintain core temperature, possibly explaining the observed upregulation of cortisol levels and alterations in metabolic markers related to renal function. In addition, thermogenesis seems to increase metabolism in brown adipose tissue, contributing to changes in nicotinamide metabolism and elevated levels of ketone bodies and acylcarnitines, these findings highlight the effectiveness of UHPLC-QTOF mass spectrometry, multivariate analysis, and pathway identification of postmortem samples in identifying metabolite markers with forensic and clinical significance. The discovered patterns may offer valuable clinical insights and diagnostic markers, emphasizing the broader potential of postmortem metabolomics in understanding critical states or diseases.

Are Aminoglycoside Antibiotics TRPing Your Metabolic Switches?

Transient receptor potential (TRP) channels are broadly implicated in the developmental programs of most tissues. Amongst these tissues, skeletal muscle and adipose are noteworthy for being essential in establishing systemic metabolic balance. TRP channels respond to environmental stimuli by supplying intracellular calcium that instigates enzymatic cascades of developmental consequence and often impinge on mitochondrial function and biogenesis. Critically, aminoglycoside antibiotics (AGAs) have been shown to block the capacity of TRP channels to conduct calcium entry into the cell in response to a wide range of developmental stimuli of a biophysical nature, including mechanical, electromagnetic, thermal, and chemical. Paradoxically, in vitro paradigms commonly used to understand organismal muscle and adipose development may have been led astray by the conventional use of streptomycin, an AGA, to help prevent bacterial contamination. Accordingly, streptomycin has been shown to disrupt both in vitro and in vivo myogenesis, as well as the phenotypic switch of white adipose into beige thermogenic status. In vivo, streptomycin has been shown to disrupt TRP-mediated calcium-dependent exercise adaptations of importance to systemic metabolism. Alternatively, streptomycin has also been used to curb detrimental levels of calcium leakage into dystrophic skeletal muscle through aberrantly gated TRPC1 channels that have been shown to be involved in the etiology of X-linked muscular dystrophies. TRP channels susceptible to AGA antagonism are critically involved in modulating the development of muscle and adipose tissues that, if administered to behaving animals, may translate to systemwide metabolic disruption. Regenerative medicine and clinical communities need to be made aware of this caveat of AGA usage and seek viable alternatives, to prevent contamination or infection in in vitro and in vivo paradigms, respectively.

The metabolic benefits of thermogenic stimulation are preserved in aging

Adipose thermogenesis has been actively investigated as a therapeutic target for improving metabolic dysfunction in obesity. However, its applicability to middle-aged and older populations, which bear the highest obesity prevalence in the US (approximately 40%), remains uncertain due to age-related decline in thermogenic responses. In this study, we investigated the effects of chronic thermogenic stimulation using the β3-adrenergic (AR) agonist CL316,243 (CL) on systemic metabolism and adipose function in aged (18-month-old) C57BL/6JN mice. Sustained β3-AR treatment resulted in reduced fat mass, increased energy expenditure, increased fatty acid oxidation and mitochondrial activity in adipose depots, improved glucose homeostasis, and a favorable adipokine profile. At the cellular level, CL treatment increased uncoupling protein 1 (UCP1)-dependent thermogenesis in brown adipose tissue (BAT). However, in white adipose tissue (WAT) depots, CL treatment increased glycerol and lipid de novo lipogenesis (DNL) and turnover suggesting the activation of the futile substrate cycle of lipolysis and reesterification in a UCP1-independent manner. Increased lipid turnover was also associated with the simultaneous upregulation of proteins involved in glycerol metabolism, fatty acid oxidation, and reesterification in WAT. Further, a dose-dependent impact of CL treatment on inflammation was observed, particularly in subcutaneous WAT, suggesting a potential mismatch between fatty acid supply and oxidation. These findings indicate that chronic β3-AR stimulation activates distinct cellular mechanisms that increase energy expenditure in BAT and WAT to improve systemic metabolism in aged mice. Our study provides foundational evidence for targeting adipose thermogenesis to improve age-related metabolic dysfunction.

The Effect of an Innovative Combination of Bergamot Polyphenolic Fraction and Cynara cardunculus L. Extract on Weight Gain Reduction and Fat Browning in Obese Mice

Obesity is one of the world's most serious public health issues, with a high risk of developing a wide range of diseases. As a result, focusing on adipose tissue dysfunction may help to prevent the metabolic disturbances commonly associated with obesity. Nutraceutical supplementation may be a crucial strategy for improving WAT inflammation and obesity and accelerating the browning process. The aim of this study was to perform a preclinical "proof of concept" study on Bergacyn®, an innovative formulation originating from a combination of bergamot polyphenolic fraction (BPF) and Cynara cardunculus (CyC), for the treatment of adipose tissue dysfunction. In particular, Bergacyn® supplementation in WD/SW-fed mice at doses of 50 mg/kg given orally for 12 weeks, was able to reduce body weight and total fat mass in the WD/SW mice, in association with an improvement in plasma biochemical parameters, including glycemia, total cholesterol, and LDL levels. In addition, a significant reduction in serum ALT levels was highlighted. The decreased WAT levels corresponded to an increased weight of BAT tissue, which was associated with a downregulation of PPARγ as compared to the vehicle group. Bergacyn® was able to restore PPARγ levels and prevent NF-kB overexpression in the WAT of mice fed a WD/SW diet, suggesting an improved oxidative metabolism and inflammatory status. These results were associated with a significant potentiation of the total antioxidant status in WD/SW mice. Finally, our data show, for the first time, that Bergacyn® supplementation may be a valuable approach to counteract adipose tissue dysfunction and obesity-associated effects on cardiometabolic risk.

The Role of Methionine-Rich Diet in Unhealthy Cerebrovascular and Brain Aging: Mechanisms and Implications for Cognitive Impairment

As aging societies in the western world face a growing prevalence of vascular cognitive impairment and Alzheimer's disease (AD), understanding their underlying causes and associated risk factors becomes increasingly critical. A salient concern in the western dietary context is the high consumption of methionine-rich foods such as red meat. The present review delves into the impact of this methionine-heavy diet and the resultant hyperhomocysteinemia on accelerated cerebrovascular and brain aging, emphasizing their potential roles in cognitive impairment. Through a comprehensive exploration of existing evidence, a link between high methionine intake and hyperhomocysteinemia and oxidative stress, mitochondrial dysfunction, inflammation, and accelerated epigenetic aging is drawn. Moreover, the microvascular determinants of cognitive deterioration, including endothelial dysfunction, reduced cerebral blood flow, microvascular rarefaction, impaired neurovascular coupling, and blood-brain barrier (BBB) disruption, are explored. The mechanisms by which excessive methionine consumption and hyperhomocysteinemia might drive cerebromicrovascular and brain aging processes are elucidated. By presenting an intricate understanding of the relationships among methionine-rich diets, hyperhomocysteinemia, cerebrovascular and brain aging, and cognitive impairment, avenues for future research and potential therapeutic interventions are suggested.

Pterostilbene Enhances Thermogenesis and Mitochondrial Biogenesis by Activating the SIRT1/PGC-1α/SIRT3 Pathway to Prevent Western Diet-Induced Obesity

SCOPE

Sirtuin 1/peroxisome proliferator-activated receptor gamma co-activator 1 alpha (SIRT1/PGC-1α) pathway activation is known to promote thermogenesis and mitochondrial biogenesis. Pterostilbene (PSB) and pinostilbene (PIN), the methylated analogs of resveratrol, are potential candidates to enhance thermogenesis and mitochondrial biogenesis.

METHOD AND RESULTS

A model of Western diet-induced obesity in mice is designed. Either PSB or PIN is supplemented in the diet for 16 weeks. Both samples can significantly reduce body weight gain but only PSB can decrease inguinal adipose tissue weight. Besides, both samples can promote lipolysis but only PSB supplementation activates the SIRT1/PGC-1α/SIRT3 pathway to enhance mitochondrial biogenesis and thermogenesis in the inguinal adipose tissue. In addition, although both samples exert a modulatory effect on gut microbiota but significant increments in fecal isobutyric acid, valeric acid, and isovaleric acid are only observed in the PSB group, functioning as gut microbial metabolites.

CONCLUSION

Overall, these findings suggest PSB and PIN as potential candidates for the improvement of obesity and gut microbiota dysbiosis. With its higher stability, PSB exerts a greater effect than PIN by promoting thermogenesis and mitochondrial biogenesis via SIRT1 activation.