Aberrant expression of thyroidal hormone receptor α exasperating mitochondrial dysfunction induced sarcopenia in aged mice.

Disrupted mitochondrial dynamics and mitophagy contribute to functional deterioration of skeletal muscle (SM) during aging, but the regulatory mechanisms are poorly understood. Our previous study demonstrated that the expression of thyroid hormone receptor α (TRα) decreased significantly in aged mice, suggesting that the alteration of thyroidal elements, especially the decreased TRα, might attenuate local THs action thus to cause the degeneration of SM with aging, while the underlying mechanism remains to be further explored. In this study, decreased expression of myogenic regulators Myf5, MyoD1, mitophagy markers Pink1, LC3II/I, p62, as well as mitochondrial dynamic factors Mfn1 and Opa1, accompanied by increased reactive oxygen species (ROS), showed concomitant changes with reduced TRα expression in aged mice. Further TRα loss- and gain-of-function studies in C2C12 revealed that silencing of TRα not only down-regulated the expression of above-mentioned myogenic regulators, mitophagy markers and mitochondrial dynamic factors, but also led to a significant decrease in mitochondrial activity and maximum respiratory capacity, as well as more mitochondrial ROS and damaged mitochondria. Notedly, overexpression of TRα could up-regulate the expression of those myogenic regulators, mitophagy markers and mitochondrial dynamic factors, meanwhile also led to an increase in mitochondrial activity and number. These results confirmed that TRα could concertedly regulate mitochondrial dynamics, autophagy, and activity, and myogenic regulators rhythmically altered with TRα expression. Summarily, these results suggested that the decline of TRα might cause the degeneration of SM with aging by regulating mitochondrial dynamics, mitophagy and myogenesis.

Serum metabolome and gut microbiome alterations are associated with low handgrip strength in older adults.

Handgrip strength (HGS), which represents global muscle strength, is a powerful indicator of disability and mortality in older adults; it is also used for the diagnosis of possible- or probable- sarcopenia and physical frailty. This study aimed to explore the metabolic mechanisms and potential biomarkers associated with declining HGS among older adults. We recruited 15 age- and environment-matched inpatients (age, 77-90 years) with low or normal HGS. Liquid chromatography-mass spectrometry (LC-MS) and 16S ribosomal DNA (rDNA) gene sequencing were performed to analyze the metabolome of serum and stool samples and the gut microbiome composition of stool samples. Spearman's correlation analysis was used to identify the potential serum and fecal metabolites associated with HGS. We assessed the levels of serum and fecal metabolites belonging to the class of cinnamic acids and derivatives and reported that the levels of carboxylic acids and their derivatives decreased in the low-HGS group. Serum levels of microbial metabolites, including cinnamoylglycine, 4-methoxycinnamic acid, and (e)-3,4,5-trimethoxycinnamic acid, were positively correlated with HGS. We found that gut microbial α-diversity was significantly higher in the low-HGS group, whereas higher ß-diversity was observed in the normal group. The relative abundances of the genera Parabacteroides and Intestinibacter increased significantly in the low-HGS group and were negatively correlated with the serum levels of cinnamoylglycine. The identified metabolites whose levels were markedly altered, and intestinal flora associated with these metabolites suggest the potential metabolic underpinnings for HGS and provide a basis for the further identification of biomarkers of muscle strength decline in older adults.

TT3, a More Practical Indicator for Evaluating the Relationship Between Sarcopenia and Thyroid Hormone in the Euthyroid Elderly Compared with FT3.

Background and Aims: Sarcopenia is a common disease in the elderly, and the thyroid hormone (TH) might participate in the pathogenesis of sarcopenia. However, the results of previous studies were not completely consistent. We performed this study to investigate the association between THs and sarcopenia in a Chinese elderly euthyroid population. Subjects and Methods: A total of 309 Chinese elderly euthyroid subjects with an average age of 85.19 ± 7.8 years were enrolled. Participants were divided into four groups (non-sarcopenia, possible sarcopenia, sarcopenia and serve sarcopenia) according to the consensus update of AWGS in 2019. Serum levels of TT3, FT3, TT4, FT4, TSH, rT3 and TBG were measured. Muscle mass was measured by multifrequency bioelectrical impedance analysis, hand grip (HG) was represented by spring-type dynamometer, and gait speed (GS) was determined by 6-metre walk test. The FRAIL scale was used to assess frailty. Results: Compared to the non-sarcopenia group, the sarcopenia group showed a significant increase in age and FRIAL score, while FT3 and TT3 levels decreased significantly. Partial correlation analysis (adjusted by age, gender and the scores of FRIAL scale) indicated that FT3, TT3 and TSH had significant positive correlations with HG, and there also was a significant positive correlation between TT3 and GS. In addition, after adjusting for age, gender, BMI, ALT, sCr, and score on the FRAIL scale, the multivariate linear regression analysis showed that TT3 was positively associated with muscle strength and negatively associated with sarcopenia risk. Conclusion: There is an association between the low TT3 level and sarcopenia. Therefore, maintaining higher T3 concentrations within the normal range appears to be beneficial for sarcopenia in the elderly. In addition, due to the fluctuation of FT3, TT3 is a more stable and practical indicator to evaluate the relationship between sarcopenia and thyroid hormone in the elderly euthyroid population.

Distinct response of adipocyte progenitors to glucocorticoids determines visceral obesity via the TEAD1-miR-27b-PRDM16 axis.

OBJECTIVE: Visceral obesity contributes to obesity-related complications; however, the intrinsic mechanism of depot-specific adipose tissue behavior remains unclear. Despite the pro-adipogenesis role of glucocorticoids (GCs) in adipogenesis, the role of GCs in visceral adiposity rather than in subcutaneous adipose tissue is not established. Because adipocyte progenitors display a striking depot-specific pattern, the regulatory pathways of novel progenitor subtypes within different depots remain unclear. This study describes a cell-specific mechanism underlying visceral adiposity. METHODS: A diverse panel of novel depot-specific adipose progenitors was screened in mice and human samples. The transcriptome distinction and various responses of novel progenitor subtypes of GCs were further measured using the GC receptor-chromatin immunoprecipitation assay and RNA sequencing. The mechanism of novel subtypes was identified using transposase-accessible chromatin analysis and bisulfite sequencing and further confirmed using precise editing of CpG methylation. RESULTS: Platelet-derived growth factor receptor α (PDGFRα+ ) progenitors, which were dominant in the visceral adipose tissue, were GC-sensitive beige adipose progenitors, whereas CD137+ progenitors, which were dominant in the subcutaneous adipose tissue, were GC-passive beige adipose progenitors. Expression of miR-27b, an inhibitor of adipocyte browning, was significantly increased in PDGFRα+ progenitors treated with GCs. Using transposase-accessible chromatin analysis, bisulfite sequencing, and precise editing of CpG methylation, TEA domain transcription factor 1 (TEAD1) was discovered to be uniquely hypomethylated in PDGFRα+ progenitors. CONCLUSIONS: GCs inhibited the PDGFRα+ progenitors' browning process via miR-27b, which was transcriptionally activated by the collaboration of TEAD1 with the GC receptor. These data provide insights into the mechanism of depot-specific variations in high-fat diet-induced obesity.

2,3',4,4',5-Pentachlorobiphenyl induced thyroid dysfunction by increasing mitochondrial oxidative stress.

Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) and are associated with thyroid diseases. Our previous study reported that 2,3',4,4',5-Pentachlorobiphenyl (PCB118) could induce thyroid dysfunction and the rat thyroid tissues exhibit abnormal mitochondrial ultrastructure. However, the more specific effects of PCB118 on mitochondria and the relationship between mitochondria and thyroid dysfunction remain unclear. In this study, Wistar rats were injected with PCB118 intraperitoneally at 0, 10, 100, and 1000 µg/kg/d for 13 weeks and FRTL-5 rat thyroid cells were treated with PCB118 (0, 0.25, 2.5, and 25 nM) for 24 hr, which did not influence the general conditions of rats and FRTL-5 cells viability. The detection of serum levels of thyroid hormones (THs) and the expression of sodium/iodide symporter (NIS) protein demonstrated that thyroid function was impaired after PCB118 exposure. Transmission electron microscopy showed mitochondrial damage in the thyroids of PCB118-treated rats. Biological processes analysis revealed that differentially expressed mRNAs in thyroid tissues induced by PCB118 were enriched in reactive oxygen species (ROS) metabolic process, hydrogen peroxide metabolic process, and hydrogen peroxide catabolic process. Moreover, mRNA expression of mitochondrial respiratory chain genes NDUFB3, UQCRC2, COX17, ATP5I and ATP5E decreased in PCB118-treated groups. In vivo and in vitro data showed that ROS production increased significantly after PCB118 exposure, accompanied by increased levels of phospho-c-Jun N-terminal kinase (P-JNK). Taken together, these results suggest that PCB118 could damage mitochondria by increasing oxidative stress and PCB118-induced thyroid dysfunction may be related to ROS-dependent activation of the JNK pathway.

Jwa participates the maintenance of intestinal epithelial homeostasis via ERK/FBXW7-mediated NOTCH1/PPARγ/STAT5 axis and acts as a novel putative aging related gene.

The intestinal epithelium is a rapid self-renewal and regenerated tissue of which the structural integrity is beneficial for maintaining health. The integrity of intestinal epithelium depends on the balance of cell proliferation, differentiation, migration, and the function of intestinal stem cells, which declines due to genetic defect or aging. Jwa participates in multiple cellular processes; it also responds to oxidative stress and repairs DNA damage. However, whether Jwa plays a role in maintaining the homeostasis of intestinal renewal and regeneration is not clear. In the present study, we firstly described that the deletion of Jwa disturbed the homeostasis of intestinal epithelial renewal and regeneration. Jwa deficiency promoted NOTCH1 degradation in the ERK/FBXW7-mediated ubiquitin-proteasome pathway, thus disturbing the PPARγ/STAT5 axis. These mechanisms might partially contribute to the reduction of intestinal stem cell function and alteration of intestinal epithelial cell lineage distribution, finally suppressing the renewal and regeneration of intestinal epithelium. Moreover, our results also revealed that Jwa was a novel putative aging related gene.

Frailty's Prevalence and the Association with Aging-Related Health Conditions in Chinese Community Dwelling Elderly.

In this paper, we have investigated the frailty's prevalence and the association with aging-related health conditions in Chinese community dwelling elderly aged ≥60 years in Lianyungang City of China. In this regard, participants were 1,072 adults aged ≥60 years from Houhe Community of Lianyungang City of China. All the enrolled participants were tested for following parameters: (1) the related risk factors of frailty: including economic status, personal health, understanding and communication skills, and mental and psychological status; (2) aging-related health conditions related to frailty: Charlson's comorbidity index (CCI), Mini Nutritional Assessment Short Form (MNA-SF), Patient Health Questionnaire-9 (PHQ-9), and Generalized Anxiety Disorder 7-item (GAD-7); (3) body composition, physical strength, and function testing: appendicular skeletal muscle mass index (ASMI), grip strength, five-repetition sit-to-stand test, 6 m walking speed, and strength assistance rise-climb-fall (SARC-F); (4) assessment of the degree and severity of frailty: physical frailty phenotype (PFP), Morse fall scale (MFS), and activities of daily living (ADL). The frailty's prevalence among the elderly aged ≥60 years in the community of Lianyungang City was 13.8%, 55.4% were prefrail, and 30.8% were robust. The independent risk factors of frailty were age, appendicular skeletal muscle mass index, sarcopenia, education, nutrition, and strength assistance rise-climb-fall (P < 0.05). Aging-related health conditions were associated with frailty, including sarcopenia, nutrition, and falls. However, mental and psychological statuses were not significantly associated with frailty.

Application of Muscle Thickness and Quality Measured by Ultrasound in Frailty Assessment in China.

To explore the correlation between Fried Frailty Phenotype (FFP) and the muscle thickness and quality of local muscle, and to provide a reasonable basis for the application of ultrasound measurement in the frailty assessment. A total of 150 people (age ≥ 65 years, 58 women, 92 men) were included from the First Hospital Affiliated to Nanjing Medical University. They were divided into Normal group (40 cases), Prefrailty group (69 cases) and Frailty group (41 cases). The thickness and the quality of local muscle were detected by ultrasound. Participants in the prefrailty group had a higher grayscale value of the vastus lateralis muscle, indicating the deterioration of muscle quality. At the frailty stage, the muscle thickness and quality of the vastus lateralis muscle and the anterior tibialis muscle decreased significantly compared with the normal and the prefrailty group. Pearson's correlation analysis also showed FFP was negatively correlated with muscle thickness and quality of the lower limbs. In multiple regression model, FFP was positively associated with gray value (Vastus lateralis muscle:ß =0.457, p < 0.001; Anterior tibialis muscle: ß = 0.220, p = 0.037) and inversely associated with muscle thickness (Vastus lateralis muscle:ß = -0.973, p = 0.031; Anterior tibialis muscle: ß = -4.551, p = 0.004) in the frailty stage. Together, FFP was closely related to muscle thickness and quality, especially vastus lateralis muscle. Moreover, Muscle quality has deteriorated in the prefrailty stage, which is earlier than muscle thickness.

Distinct Serum and Fecal Metabolite Profiles Linking With Gut Microbiome in Older Adults With Frailty.

Frailty is a critical aging-related syndrome but the underlying metabolic mechanism remains poorly understood. The aim of this study was to identify novel biomarkers and reveal potential mechanisms of frailty based on the integrated analysis of metabolome and gut microbiome. In this study, twenty subjects consisted of five middle-aged adults and fifteen older adults, of which fifteen older subjects were divided into three groups: non-frail, pre-frail, and frail, with five subjects in each group. The presence of frailty, pre-frailty, or non-frailty was established according to the physical frailty phenotype (PFP). We applied non-targeted metabolomics to serum and feces samples and used 16S rDNA gene sequencing to detect the fecal microbiome. The associations between metabolites and gut microbiota were analyzed by the Spearman's correlation analysis. Serum metabolic shifts in frailty mainly included fatty acids and derivatives, carbohydrates, and monosaccharides. Most of the metabolites belonging to these classes increased in the serum of frail older adults. Propylparaben was found to gradually decrease in non-frail, pre-frail, and frail older adults. Distinct changes in fecal metabolite profiles and gut microbiota were also found among middle-aged adults, non-frail and frail older subjects. The relative abundance of Faecalibacteriu, Roseburia, and Fusicatenibacter decreased while the abundance of Parabacteroides and Bacteroides increased in frailty. The above altered microbes were associated with the changed serum metabolites in frailty, which included dodecanedioic acid, D-ribose, D-(-)-mannitol, creatine and indole, and their related fecal metabolites. The changed microbiome and related metabolites may be used as the biomarkers of frailty and is worthy of further mechanistic studies.

Age-Related Changes in Trabecular Bone Score and Bone Mineral Density in Chinese Men: A Cross-Sectional and Longitudinal Study.

Purpose: This study was designed to explore age-related changes in trabecular bone score (TBS) and bone mineral density (BMD) in Chinese men through cross-sectional and longitudinal studies. Patients and Methods: We included adult men who had at least twice TBS and BMD examinations in our hospital between January 2013 and December 2020. All men were divided into an age subgroup per 10 years, comparing differences in baseline lumbar spine (LS) TBS and BMD at various parts between each age group and analyzing age-related changes in TBS and BMD during follow-up. Results: Baseline data showed that in men aged 36 to 85 years, BMD in the hip region showed a decreasing trend with age (P for trend < 0.01). However, TBS reached a high value around the age of 50, after which it decreased with age (P for trend = 0.03). During a mean follow-up of 3 years, the average annual change rate at TBS was -0.17% in men aged 36 to 85 years, with the fastest decrease rate -1.08% at 66 to 75 years (P < 0.05). The mean annual rate of change in LS BMD in different age subgroups increased with age (P for trend = 0.001). There was no significant decrease in mean annual change in BMD in hip regions. Conclusion: In men aged 36~85 years, the trend of TBS was inconsistent with BMD. Men experience a high value of LS TBS around age 50, later than the commonly believed age of peak BMD, which may reflect developmental differences between bone microstructure and bone minerals. The TBS may be used as a better indicator of changes in bone strength than BMD in adult men at short-term follow-up. The rapid loss of TBS at age 66 to 75 may have implications for the prevention and medication of osteoporosis in men.

Estrogen supplementation deteriorates visceral adipose function in aged postmenopausal subjects via Gas5 targeting IGF2BP1.

Increased visceral fat is strongly associated with a series of metabolic complications. Postmenopausal women have an increased risk of visceral fat accumulation, metabolic disorders, and a high incidence of cardiovascular events. However, the effect of estrogen replacement therapy on visceral adipose tissue among postmenopausal women of different ages remains controversial, and the underlying mechanism remains unclear. Hence, it is important to understand when estrogen replacement therapy affects the function of visceral adipose tissue (VAT). Therefore, we collected VAT from pre- and post-menopausal females and we observed increased pro-inflammatory cytokines and insulin resistance-inducing factors, decreased insulin-sensitizing factors, and thermogenic factors in VAT of postmenopausal women. The analysis of adipocytes isolated from the VAT of females of different ages indicated that adiponectin and browning signature genes were significantly decreased with estrogen treatment in postmenopausal women, but were not altered in the young group. Estrogen supplementation in aged female mice (22 m) significantly prevented visceral fat accumulation. However, it deteriorated VAT function by inducing pro-inflammatory cytokines and insulin resistance-inducing factors and decreasing insulin-sensitizing and thermogenic factors. Mechanistically, estrogen induced the expression of long non-coding RNA Gas5 via binding ERα in premenopausal women, which therefore suppressed IGF2BP1 to maintain VAT function. After menopause, with the reversal of ERα/ERß ratio in VAT, estrogen supplementation mainly worked through ERß, which led to low expression levels of Gas5 and eventually caused VAT dysfunction. Our study demonstrated the adverse effects of estrogen supplementation on VAT function in aged postmenopausal population and further elucidated the involved mechanism.

2,3',4,4',5-Pentachlorobiphenyl attenuated fast-twitch fibers and fiber size of skeletal muscle via disturbing thyroid hormone signaling and mitochondrial dynamics.

Polychlorinated biphenyls (PCBs) affect multiple organs, and some of the effects are mediated by interfering with thyroid hormone (TH) signaling that regulates physiological processes in mammals. It remains unclear how PCBs affect skeletal muscle (SM). In our study, wistar rats were injected 2,3',4,4',5-pentachlorobiphenyl (PCB118) intraperitoneally at 0, 10, 100, and 1000 µg/kg/day for 13 weeks, and C2C12 myoblasts were treated PCB118 (0, 0.25, 25, and 50 nM) for 24 h or 48 h. We found that myocyte cross-sectional area (MCSA) was reduced, MyHC IIa and MyHC IIb mRNA levels significantly decreased, and muscle strength was weakened in PCB118-exposed rats. TH receptor α (TRα) and iodothyronine deiodinase type 2 (DIO2) were upregulated after PCB118 exposure both in vivo and in vitro. Transmission electron microscopy showed significant mitochondrial abnormalities in PCB118-treated rats, and the expression of mitochondrial regulators such as PTEN-induced kinase 1 (PINK1) and GTPase dynamin-related protein 1 (DRP1) were altered after PCB118 exposure. These results suggest that PCB118 could weaken muscle strength and attenuate fast-twitch fibers and fiber size of SM in rats. TH signaling, mitochondrial dynamics and mitophagy were also disturbed by PCB118, which may contribute to the alternations of SM structure and function.

Caloric restriction delays age-related muscle atrophy by inhibiting 11ß-HSD1 to promote the differentiation of muscle stem cells.

Introduction: Calorie restriction (CR) is an important direction for the delay of sarcopenia in elderly individuals. However, the specific mechanisms of CR against aging are still unclear. Methods: In this study, we used a CR model of elderly mice with muscle-specific 11ß-hydroxysteroid dehydrogenase 1 (11ß-HSD1) knockout mice and 11ß-HSD1 overexpression mice to confirm that CR can delay muscle aging by inhibiting 11ß-HSD1 which can transform inactive GC(cortisone) into active GC(cortisol). The ability of self-proliferation and differentiation into muscle fibers of these mouse muscle stem cells (MuSCs) was observed in vitro. Additionally, the mitochondrial function and mitochondrial ATP production capacity of MuSCs were measured by mitochondrial oxygen consumption. Results: It was found that the 11ß-HSD1 expression level was increased in age-related muscle atrophy. Overexpression of 11ß-HSD1 led to muscle atrophy in young mice, and 11ß-HSD1 knockout rescued age-related muscle atrophy. Moreover, CR in aged mice reduced the local effective concentration of glucocorticoid (GC) through 11ß-HSD1, thereby promoting the mitochondrial function and differentiation ability of MuSCs. Conclusions: Together, our findings highlight promising sarcopenia protection with 40% CR in older ages. Furthermore, we speculated that targeting an 11ß-HSD1-dependent metabolic pathway may represent a novel strategy for developing therapeutics against age-related muscle atrophy.

Selective Inhibition of 11ß-Hydroxysteroid Dehydrogenase Type 1 Attenuates High-Fat Diet-Induced Hepatic Steatosis in Mice.

INTRODUCTION: The effect of 11ß-hydroxysteroid dehydrogenase type1 (11ß-HSD1) inhibition on hepatic steatosis is incompletely understood. Here, we aimed to determine the therapeutic effect of BVT.2733, a selective 11ß-HSD1 inhibitor, on hepatic steatosis. MATERIALS AND METHODS: C57B/6J mice were randomly divided into a low-fat diet (LFD) fed group and a high-fat diet (HFD) fed group. Mice were fed with HFD for 28 weeks which induced obesity and severe hepatic steatosis. The two groups were further divided into four groups as follows: LFD, LFD with BVT.2733, HFD, and HFD with BVT.2733. Mice in LFD+BVT and HFD+BVT groups were intraperitoneally injected with BVT.2733 daily for 30 days. Effects of BVT.2733 on mice body weight, serum lipid profile, serum free fatty acids (FFAs), glucocorticoid levels, gene expression in adipose and liver tissues were assessed. RESULTS: Injection of a low dose of BVT.2733 (50 mg/kg/day) reduced body weight and hyperlipidemia, but did not improve glucose tolerance and insulin resistance in diet-induced obese mice. The low dose of BVT.2733 attenuated hepatic steatosis, liver injury, and liver lipolytic gene expression in diet-induced obese mice. Besides, the low dose of BVT.2733 reduced fat mass and lipolysis in visceral adipose tissues, hepatic FFAs, and serum corticosterone levels in diet-induced obese mice. CONCLUSION: Our study shows that moderate inhibition of 11ß-HSD1 by BVT.2733 reduces FFAs and corticosterone synthesis in fatty tissues, thereby attenuates the delivery of corticosterone and FFAs to the liver. Collectively, this prevents high-fat diet-induced hepatic steatosis.

Mechanism of thyroid hormone signaling in skeletal muscle of aging mice.

BACKGROUND AND AIM: Skeletal muscle (SM) has been shown as a target of thyroid hormones (THs). However, the status of TH signaling in aged SM remains unclear. This study aimed to explore the mechanism of TH signaling in SM of aging mice. METHODS: Thirty C57BL/6J male mice were divided into 6-, 15- and 22-month (6, 15 and 22M) groups according to different age. Physical parameters were evaluated by analytical balance, grip strength test and histological analysis. Thyroid function was detected by enzyme-linked immunosorbent assay. TH signaling was compared among the three groups by real-time PCR and western blotting analysis. RESULTS: p16, p21, and p53 mRNA levels in SM increased in age-dependent manner. The muscle weight and strength decreased in 22M group compared to 6 and 15M groups. Concentrations of thyroid hormones, including free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) in 22 M mice were not shown significant difference compared to 6M or 15M mice, although FT3 showed slightly decrease and TSH appeared a mild increase accompanying with age. mRNA levels of TH transporters, including MCT8 and MCT10, as well as iodothyronine deiodinase type 2 (DIO2) and type 3 (DIO3), were higher in 22M, while TH receptor α (TRα) mRNA and protein expression was lower in 22M, compared to the other groups. Type-I myosin heavy chain (MyHC I), MyHC IIx, and MyHC IIa were upregulated and Type-IIb MyHC (MyHC IIb) was downregulated in SM with advancing age. CONCLUSIONS: TH signaling in SM changes with aging.

Differential Responses of White Adipose Tissue and Brown Adipose Tissue to Calorie Restriction During Aging.

Age-related adipose tissue dysfunction is potentially important in the development of insulin resistance and metabolic disorder. Caloric restriction (CR) is a robust intervention to reduce adiposity, improve metabolic health, and extend healthy life span. Both white adipose tissue (WAT) and brown adipose tissue (BAT) are involved in energy homeostasis. CR triggers the beiging of WAT in young mice; however, the effects of CR on beiging of WAT and function of BAT during aging are unclear. This study aimed to investigate how age and CR impact the beiging of WAT, the function of BAT, and metabolic health in mice. C57BL/6 mice were fed CR diet (40% less than the ad libitum [AL] diet) for 3 months initiated in young (3 months), middle-aged (12 months), and old (19 months) stage. We found age-related changes in different types of adipose tissue, including adipocyte enlargement, declined beiging of WAT, and declined thermogenic and ß-oxidational function of BAT. Moreover, CR attenuated age-associated adipocyte enlargement and prevented the age-related decline in beiging potential of WAT. These protective effects on the beiging potential were significant in inguinal WAT at all three ages, which were significant in epididymal WAT at young and old age. In contrast, thermogenic and ß-oxidational function of BAT further declined after CR in the young age group. In conclusion, our findings reveal the contribution of WAT beiging decline to age-related metabolic disorder and suggest nutritional intervention, specifically targeting WAT beiging, as an effective approach to metabolic health during aging.

Measurement of BAT activity by targeted molecular magnetic resonance imaging.

OBJECTIVE: The aim of this study was to measure brown adipose tissue (BAT) activity by targeted peptide (CKGGRAKDC-NH2)-coupled, polyethylene glycol (PEG)-coated ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles with magnetic resonance imaging (MRI). METHODS: The peptide was conjugated with PEG-coated USPIO to obtain targeted probes. Male C57BL/6 J mice were randomly divided into cold exposing and control group (n = 5 per group). T2*-weighted images were obtained pre- and post-contrast probes. Histological and gene expression analyses were carried out. RESULTS: T2* relaxation time of BAT in the cold exposing group decreased more significantly compared to the control group. The calculated R2* increased with the reduction of T2* value. The ΔR2* (26.68 s-1) of BAT in the cold exposing group was significantly higher (P < 0.05) than the control group. Iron particle sediments in BAT of the cold exposing group were revealed more than the control group with Prussian blue staining. The UCP1 expression level was up-regulated after cold activation. CONCLUSIONS: BAT activity could be measured in vivo by the targeted peptide-coupled, PEG-coated USPIOs with MRI.

Improvement of intestinal stem cells and barrier function via energy restriction in middle-aged C57BL/6 mice.

This study aimed to reveal the impact of energy restriction on the intestine via structural and molecular changes in terms of intestinal stem cell (ISC) function, ISC niche, intestinal epithelial barrier function, and intestinal immune function. Female C57BL/6J mice, aged 12 months, fed a commercial chow were used in this study. The ISC function, ISC niche, intestinal epithelial barrier function, and intestinal immune function were assessed. Energy restriction reversed aging-induced intestinal shortening and made the crypts shallower. The intestinal epithelial cells isolated from the intestine showed a significant increase in the expression levels of stem cell-associated genes in small intestinal epithelial cells as detected by flow cytometry. Despite the increase in the number of stem cells and the expression levels of markers, no increase or decrease was found in the enteroid complexity of the small intestine and colonic enteroid formation in vitro. The colonic mucous layer was measured in mice of the energy restricted (ER)-treated group to investigate the epithelial barrier function in the colon. The results revealed that the barrier was more complete. The fluorescence intensity of tight junction markers claudin-2 and zonula occludens-1 increased and the mRNA expression profiles of monocyte chemotactic protein 1 and interleukin-6 decreased in the colon of mice in the ER-treated group. The beneficial effects of ER on the colon in terms of the integrity of the mucosal barrier and alleviation of inflammation were confirmed, thus highlighting the importance of modulating the intestinal function in developing effective antiaging dietary interventions.

2,3',4,4',5-Pentachlorobiphenyl Induced Thyrocyte Autophagy by Promoting Calcium Influx via Store-Operated Ca2+ Entry.

PCB118, a 2,3',4,4',5-pentachlorobiphenyl, has been shown to destroy thyroidal ultrastructure and induce thyrocyte autophagy. Previously, we reported that PCB118 promoted autophagosome formation in vivo and in vitro, but more details remain to be revealed. To explore the underlying mechanism by which PCB118 regulates thyrocyte autophagy, Fischer rat thyroid cell line-5 (FRTL-5) cells were exposed to different doses of PCB118 at 0, 0.25, 2.5, and 25 nM for 0-48 h. Western blot analysis of autophagy-related proteins P62, BECLIN1, and LC3 demonstrated that PCB118 induced autophagy formation in dose- and time-dependent manner. Moreover, laser scanning confocal microscopy and flow cytometry showed PCB118 treatment led to time- and dose-dependent increase in intracellular calcium concentration ([Ca2+]i). Additionally, PCB118 promoted store-operated Ca2+ entry (SOCE) channel followed by significant increase of ORAI1 and STIM1 protein levels. On the other hand, PCB118 induced thyroidal autophagy via class III ß-tubulin (TUBB3)/death-associated protein kinase 2 (DAPK2)/myosin regulatory light chain (MRLC)/autophagy-related 9A (ATG9A) pathway in FRTL-5 cells. Pretreatment with SOCE inhibitor SKF96365 reduced cytosolic Ca2+, ORAI1, STIM1, and BECLIN1 levels as well as LC3 II/LC3 I ratio, while increased P62 expression. SKF96365 also inhibited TUBB3/DAPK2/MRLC/ATG9A pathway in FRTL-5 cells treated by PCB118. Our results provide evidence that PCB118 may induce thyroidal autophagy through TUBB3-related signaling pathway, and these effects are likely to be regulated by calcium influx via SOCE channel.

Impact of a high­fat diet on intestinal stem cells and epithelial barrier function in middle­aged female mice.

A high­fat diet (HFD) or obesity­promoting diet is closely associated with metabolic diseases and intestinal tumors, particularly in middle­aged individuals (typically 45­64 years old). The intestinal epithelium constitutes a barrier that separates the host from the food and microbiota in the gut, and thus, a dysfunctional epithelium is associated with a number of diseases. However, the changes caused to the function of intestinal epithelium in response to an HFD have not been well­studied to date. In the present study, middle­aged female mice (12 months old) fed an HFD for a period of 14 weeks were used to determine the effects of HFD on the intestine. Characteristics including the body weight, fat deposition, glucose metabolism, inflammatory state and intestinal morphology were assessed, while the intestinal stem cell (ISC) counts and the ability of isolated intestinal crypts to form organoid bodies in 3D culture were examined. Intestinal epithelial barrier function, including secretory defense, tight junctions and cell apoptosis, were also studied. Morphologically, the HFD resulted in a mild reduction in the length of villi of the small intestine, the colon length and the depth of colon crypts. In addition, the ISC counts were increased in the small intestine and colon in HFD­fed mice. The ability of crypts to grow into organoids (mini­guts) was also increased in crypts obtained from mice fed an HFD, while HFD compromised the epithelial barrier function of the colon. These results demonstrated how an HFD affects the intestinal epithelium and highlighted the need to carefully consider dietary patterns.