Adipose tissue and age‑dependent insulin resistance: New insights into WAT browning (Review)

Eriodictyol regulates white adipose tissue browning and hepatic lipid metabolism in high fat diet-induced obesity mice via activating AMPK/SIRT1 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Blossom of Citrus aurantium L. var. amara Engl. (CAVA) has been popularly consumed as folk medicine and dietary supplement owing to its various beneficial effects and especially anti-obesity potential. Our previous study predicted that eriodictyol was probably one of the key active compounds of the total flavonoids from blossom of CAVA. However, effects of eriodictyol in anti-obesity were still elusive.

AIM OF THE STUDY

This study was performed to explore the precise role of eriodictyol in white adipose tissue (WAT) browning and hepatic lipid metabolism, and simultaneously, to verify the impact of eriodictyol on the total flavonoids of CAVA in losing weight.

MATERIALS AND METHODS

The pancreas lipase assay was conducted and oleic acid-induced HepG2 cells were established to preliminarily detect the lipid-lowering potential of eriodictyol. Then, high fat diet-induced obesity (DIO) mouse model was established for in vivo studies. The biochemical indicators of mice were tested by commercial kits. The histopathological changes of WAT and liver in mice were tested by H&E staining, Oil Red O staining and Sirius Red staining. Immunohistochemical, Western blot assay, as well as RT-qPCR analysis were further performed. Additionally, molecular docking assay was used to simulate the binding of eriodictyol with potential target proteins.

RESULTS

In vitro studies showed that eriodictyol intervention potently inhibited pancreatic lipase activity and reversed hepatic steatosis in oleic acid-induced HepG2 cells. Consistently, long-term medication of eriodictyol also effectively prevented obesity and improved lipid and glucose metabolism in diet-induced obesity mice. Obesity-induced histopathological changes in iWAT, eWAT and BAT, and abnormal expression levels of IL-10, IL-6 and TNF-α in iWAT of DIO mice were also significantly reversed by eriodictyol treatment. Eriodictyol administration significantly and potently promoted browning of iWAT by increasing expression levels of thermogenic marker protein of UCP1, as well as brown adipocyte-specific genes of PGC-1α, SIRT1 and AMPKα1. Further assays revealed that eriodictyol enhanced mitochondrial function, as shown by an increase in compound IV activity and the expression of tricarboxylic acid cycle-related genes. Besides, eriodictyol addition markedly reversed hepatic damages and hepatic inflammation, and enhanced hepatic lipid metabolism in DIO mice, as evidenced by its regulation on p-ACC, CPT1-α, UCP1, PPARα, PGC-1α, SIRT1 and p-AMPKα expression. Molecular docking results further validated that AMPK/SIRT1 pathway was probably the underlying mechanisms by which eriodictyol acted.

CONCLUSION

Eriodictyol exhibited significant anti-obesity effect, which was comparable to that of the total flavonoids from blossom of CAVA. These findings furnished theoretical basis for the application of eriodictyol in weight loss.

Vascular Aging and Atherosclerosis: A Perspective on Aging

Vascular aging (VA) is recognized as a pivotal factor in the development and progression of atherosclerosis (AS). Although various epidemiological and clinical research has demonstrated an intimate connection between aging and AS, the candidate mechanisms still require thorough examination. This review adopts an aging-centric perspective to deepen the comprehension of the intricate relationship between biological aging, vascular cell senescence, and AS. Various aging-related physiological factors influence the physical system's reactions, including oxygen radicals, inflammation, lipids, angiotensin II, mechanical forces, glucose levels, and insulin resistance. These factors cause endothelial dysfunction, barrier damage, sclerosis, and inflammation for VA and promote AS via distinct or shared pathways. Furthermore, the increase of senescent cells inside the vascular tissues, caused by genetic damage, dysregulation, secretome changes, and epigenetic modifications, might be the primary cause of VA.

The effect of insulin resistance in the association between obesity and hypertension incidence among Chinese middle-aged and older adults: data from China health and retirement longitudinal study (CHARLS)

Background and aims

Obesity and insulin resistance are well-known important risk factors for hypertension. This study aimed to investigate the mediating effect of the triglyceride-glucose index (TyG) in the association between Chinese visceral obesity index (CVAI) and hypertension among Chinese middle-aged and older adults.

Methods

A total of 10,322 participants aged 45 years and older from CHARLS (2011-2018) were included. Baseline data were collected in 2011 and hypertension incidence data were gathered during follow-up in 2013, 2015 and 2018. Multivariate logistic regression models were constructed to investigate the association of CVAI and TyG with the incidence of hypertension. Additionally, mediation analyses were conducted to evaluate the mediating role of the TyG index in the relationship between CVAI and hypertension. Subgroup analysis was also performed.

Results

A total of 2,802 participants developed hypertension during the follow-up period. CVAI and TyG index were independently and significantly associated with hypertension incidence. Increasing quartiles of CVAI and TyG index were associated with high hypertension incidence in middle-aged and older adults. The TyG index was identified as a mediator in the relationship between CVAI and hypertension incidence, with a mediation effect (95% confidence interval) was 12.38% (6.75, 31.81%).

Conclusion

Our study found that CVAI and TyG were independently associated with hypertension incidence. TyG played a partial mediating effect in the positive association between CVAI and hypertension incidence.

Senescent adipocytes and type 2 diabetes - current knowledge and perspective concepts

Among civilization diseases, the number of individuals suffering from type 2 diabetes (T2DM) is expected to increase to more than a billion in less than 20 years, which is associated with, e.g., populational aging, poor diet, sedentary lifestyle, genetic predispositions, and immunological factors. T2DM affects many organs and is characterized by insulin resistance, high glucose levels, and adipocyte dysfunction, which are related to senescence. Although this type of cellular aging has beneficial biological functions, it can also act unfavorable since senescent adipocytes resist apoptosis, enhance cytokine secretion, downregulate cell identity genes, and acquire the senescence-associated secretory phenotype that renders a more oxidative environment. Opposing T2DM is possible via a wide variety of senotherapies, including senolytics and senomorphics; nevertheless, further research is advised to expand therapeutic possibilities and benefits. Consequences that ought to be deeply researched include secretory phenotype, chronic inflammation, increasing insulin resistance, as well as impairment of adipogenesis and functioning of adipocyte cells. Herein, despite reviewing T2DM and fat tissue senescence, we summarized the latest adipocyte-related anti-diabetes solutions and suggested further research directions.

Roles of Protein Post-Translational Modifications During Adipocyte Senescence

Adipocytes are adipose tissues that supply energy to the body through lipids. The two main types of adipocytes comprise white adipocytes (WAT) that store energy, and brown adipocytes (BAT), which generate heat by burning stored fat (thermogenesis). Emerging evidence indicates that dysregulated adipocyte senescence may disrupt metabolic homeostasis, leading to various diseases and aging. Adipocytes undergo senescence via irreversible cell-cycle arrest in response to DNA damage, oxidative stress, telomere dysfunction, or adipocyte over-expansion upon chronic lipid accumulation. The amount of detectable BAT decreases with age. Activation of cell cycle regulators and dysregulation of adipogenesis-regulating factors may constitute a molecular mechanism that accelerates adipocyte senescence. To better understand the regulation of adipocyte senescence, the effects of post-translational modifications (PTMs), is essential for clarifying the activity and stability of these proteins. PTMs are covalent enzymatic protein modifications introduced following protein biosynthesis, such as phosphorylation, acetylation, ubiquitination, or glycosylation. Determining the contribution of PTMs to adipocyte senescence may identify new therapeutic targets for the regulation of adipocyte senescence. In this review, we discuss a conceptual case in which PTMs regulate adipocyte senescence and explain the mechanisms underlying protein regulation, which may lead to the development of effective strategies to combat metabolic diseases.

Evaluation of serum telomerase activity in normal-weight young girls with polycystic ovary syndrome and its relation to metabolic parameters

OBJECTIVES

This study investigated the discriminative value of serum telomerase levels in polycystic ovary syndrome (PCOS) and its relation to metabolic parameters.

METHODS

Patients aged 16-23 years old who visited an adolescent outpatient clinic were included in the study. Our study consisted of 45 non-obese girls with polycystic ovary syndrome (PCOS), while our control group consisted of 45 healthy girls with normal menstrual cycles and no signs of hyperandrogenism. During the early follicular phase, all individuals were analyzed for serum telomerase levels, blood cell count, biochemical parameters, basal hormone levels, lipid profile and homeostatic model assessment of insulin resistance (HOMA-IR) index.

RESULTS

Serum telomerase levels in PCOS patients were considerably lower (80.0 ± 52.8 IU/mL) than in the controls (113.1 ± 54.9 IU/mL) (p=0.004). We observed that blood telomerase levels less than 108.6 distinguished PCOS group from healthy controls with a sensitivity of 73.33% and a specificity of 57.78%. Low-density lipoprotein cholesterol, HOMA-IR index, Ferriman-Gallwey score and dehydroepiandrosterone sulfate values were higher in the study group. Moreover, serum telomerase levels were inversely correlated with body mass index (r=-0.339, p=0.023) and triglycerides (r=-0.511, p=0.002) in this group. Telomerase levels were also considerably lower in patients with metabolic syndrome (p=0.005).

CONCLUSIONS

Serum telomerase activity is lower in PCOS patients than in healthy controls. Furthermore, decreased serum telomerase levels may correlate well with the metabolic complications of PCOS.

Effects of a maternal high-fat diet on adipose tissue in murine offspring: A systematic review and meta-analysis

The aim of this systematic review and meta-analysis was to analyze the influence of a maternal and/or offspring high-fat diet (HFD) on the morphology of the offspring adipocytes and amount of food and energy consumption. The search was conducted through Pubmed, EMBASE, and Web of Science databases up to October 31st, 2021. The outcomes were extracted and pooled as a standardized mean difference with random effect models. 5,004 articles were found in the databases. Of these, only 31 were selected for this systematic review and 21 were included in the meta-analysis. A large discrepancy in the percentage of fat composing the HFD (from 14% to 62% fat content) was observed. Considering the increase of adipose tissue by hyperplasia (cell number increase) and hypertrophy (cell size increase) in HFD models, the meta-analysis showed that excessive consumption of a maternal HFD influences the development of visceral white adipose tissue in offspring, related to adipocyte hypertrophy, regardless of their HFD or control diet consumption. Upon following a long-term HFD, hyperplasia was confirmed in the offspring. When analyzing the secondary outcome in terms of the amount of food and energy consumed, there was an increase of caloric intake in the offspring fed with HFD whose mothers consumed HFD. Furthermore, the adipocyte hypertrophy in different regions of the adipose tissue is related to the sex of the pups. Thus, the adipose tissue obesity phenotypes in offspring are programmed by maternal consumption of a high-fat diet, independent of postnatal diet.

Citrate enrichment in a Western diet reduces weight gain via browning of adipose tissues without resolving diet-induced insulin resistance in mice

Citrate, a major component of processed foods, reduces weight gain without resolving insulin resistance.

Prevalence of prediabetes in adults and its association with sociodemographic, nutritional, metabolic and mental disorders factors: Home Health Survey, Piauí, Brazil

ABSTRACT Objective To estimate prevalence of prediabetes and to investigate its associated factors in adults living in Teresina, Piauí, Brazil Methods Cross-sectional, home-based study, with both genders adults in Teresina, Piauí. The prevalence of prediabetes was estimated using the fasting glucose test, and was classified according to the American Diabetes Association standards (≥100mg/dL; <126mg/dL). The associations between prediabetes and the variables: sociodemographic, anthropometric, food consumption, blood pressure levels, triglycerides and common mental disorders were tested. In addition, a variable was created to verify the association of the simultaneous presence of risk factors in the same individual. Data were reviewed using Pearson’s chi-square test and Poisson regression for crude and adjusted prevalence ratios, considering a significance level of 5%. Results A total of 224 adults participated in the study, of which 154 (68.7%) were female, aged between 20 and 39 years (53.1%). An 8.04% prevalence of prediabetes was observed. A statistically significant association (p<0.05) was found between lower education (0 to 8 years of study; 17.3%) and increased triglycerides levels (≥150mg/dL; 13.7%). Higher gross prevalence (PR: 2.53; CI 95%: 1.05-6.05) prediabetes ratios were observed with 5 or more simultaneous risk factors when compared to individuals who had up to 4 simultaneous risk factors. Conclusion Low schooling, hypertriglyceridemia and the presence of five or more simultaneous risk factors were associated with prediabetes; however, these risk factors are subject to intervention. Therefore, this study points to the need for changes in lifestyle habits as a strategy for glycemic control and diabetes prevention.

Food phenolics stimulate adipocyte browning via regulating gut microecology

Fat browning has piqued the interest of researchers as a potential target for treating obesity and related metabolic disorders. Recruitment of brown adipocytes leads to enhanced energy dissipation and reduced adiposity, thus facilitating the maintenance of metabolic homeostasis. Evidence is increasing to support the crucial roles of polyphenols and gut microecology in turning fat "brown". However, it is not clear whether the intestinal microecology is involved in polyphenol-mediated regulation of adipose browning, so this concept is worthy of exploration. In this review, we summarize the current knowledge, mostly from studies with murine models, supporting the concept that the effects of food phenolics on brown fat activation and white fat browning can be attributed to their regulatory actions on gut microecology, including microbial community profile, gut metabolites, and gut-derived hormones. Furthermore, the potential underlying pathways involved are also discussed. Basically, understanding gut microecology paves the way to determine the underlying roles and mechanisms of food phenolics in adipose browning.