Induction of Dbp by a histone deacetylase inhibitor is involved in amelioration of insulin sensitivity via adipocyte differentiation in ob/ob mice

Circadian Dysfunction in Adipose Tissue: Chronotherapy in Metabolic Diseases

Essential for survival and reproduction, the circadian timing system (CTS) regulates adaptation to cyclical changes such as the light/dark cycle, temperature change, and food availability. The regulation of energy homeostasis possesses rhythmic properties that correspond to constantly fluctuating needs for energy production and consumption. Adipose tissue is mainly responsible for energy storage and, thus, operates as one of the principal components of energy homeostasis regulation. In accordance with its roles in energy homeostasis, alterations in adipose tissue's physiological processes are associated with numerous pathologies, such as obesity and type 2 diabetes. These alterations also include changes in circadian rhythm. In the current review, we aim to summarize the current knowledge regarding the circadian rhythmicity of adipogenesis, lipolysis, adipokine secretion, browning, and non-shivering thermogenesis in adipose tissue and to evaluate possible links between those alterations and metabolic diseases. Based on this evaluation, potential therapeutic approaches, as well as clock genes as potential therapeutic targets, are also discussed in the context of chronotherapy.

Single-cell dissection of the obesity-exercise axis in adipose-muscle tissues implies a critical role for mesenchymal stem cells

Exercise training is critical for the prevention and treatment of obesity, but its underlying mechanisms remain incompletely understood given the challenge of profiling heterogeneous effects across multiple tissues and cell types. Here, we address this challenge and opposing effects of exercise and high-fat diet (HFD)-induced obesity at single-cell resolution in subcutaneous and visceral white adipose tissue and skeletal muscle in mice with diet and exercise training interventions. We identify a prominent role of mesenchymal stem cells (MSCs) in obesity and exercise-induced tissue adaptation. Among the pathways regulated by exercise and HFD in MSCs across the three tissues, extracellular matrix remodeling and circadian rhythm are the most prominent. Inferred cell-cell interactions implicate within- and multi-tissue crosstalk centered around MSCs. Overall, our work reveals the intricacies and diversity of multi-tissue molecular responses to exercise and obesity and uncovers a previously underappreciated role of MSCs in tissue-specific and multi-tissue beneficial effects of exercise.

Peroxisome Proliferator-Activated Receptor Activation in Precision-Cut Bovine Liver Slices Reveals Novel Putative PPAR Targets in Periparturient Dairy Cows

Metabolic challenges experienced by dairy cows during the transition between pregnancy and lactation (also known as peripartum), are of considerable interest from a nutrigenomic perspective. The mobilization of large amounts of non-esterified fatty acids (NEFA) leads to an increase in NEFA uptake in the liver, the excess of which can cause hepatic accumulation of lipids and ultimately fatty liver. Interestingly, peripartum NEFA activate the Peroxisome Proliferator-activated Receptor (PPAR), a transcriptional regulator with known nutrigenomic properties. The study of PPAR activation in the liver of periparturient dairy cows is thus crucial; however, current in vitro models of the bovine liver are inadequate, and the isolation of primary hepatocytes is time consuming, resource intensive, and prone to errors, with the resulting cells losing characteristic phenotypical traits within hours. The objective of the current study was to evaluate the use of precision-cut liver slices (PCLS) from liver biopsies as a model for PPAR activation in periparturient dairy cows. Three primiparous Jersey cows were enrolled in the experiment, and PCLS from each were prepared prepartum (−8.0 ± 3.6 DIM) and postpartum (+7.7± 1.2 DIM) and treated independently with a variety of PPAR agonists and antagonists: the PPARα agonist WY-14643 and antagonist GW-6471; the PPARδ agonist GW-50156 and antagonist GSK-3787; and the PPARγ agonist rosiglitazone and antagonist GW-9662. Gene expression was assayed through RT-qPCR and RNAseq, and intracellular triacylglycerol (TAG) concentration was measured. PCLS obtained from postpartum cows and treated with a PPARγ agonist displayed upregulation of ACADVL and LIPC while those treated with PPARδ agonist had increased expression of LIPC, PPARD, and PDK4. In PCLS from prepartum cows, transcription of LIPC was increased by all PPAR agonists and NEFA. TAG concentration tended to be larger in tissue slices treated with PPARδ agonist compared to CTR. Use of PPAR isotype-specific antagonists in PCLS cultivated in autologous blood serum failed to decrease expression of PPAR targets, except for PDK4, which was confirmed to be a PPARδ target. Transcriptome sequencing revealed considerable differences in response to PPAR agonists at a false discovery rate-adjusted p-value of 0.2, with the most notable effects exerted by the PPARδ and PPARγ agonists. Differentially expressed genes were mainly related to pathways involved with lipid metabolism and the immune response. Among differentially expressed genes, a subset of 91 genes were identified as novel putative PPAR targets in the bovine liver, by cross-referencing our results with a publicly available dataset of predicted PPAR target genes, and supplementing our findings with prior literature. Our results provide important insights on the use of PCLS as a model for assaying PPAR activation in the periparturient dairy cow.

A Transcriptomic Response to Lactiplantibacillus plantarum-KCC48 against High-Fat Diet-Induced Fatty Liver Diseases in Mice

The most prevalent chronic liver disorder in the world is fatty liver disease caused by a high-fat diet. We examined the effects of Lactiplantibacillus plantarum-KCC48 on high-fat diet-induced (HFD) fatty liver disease in mice. We used the transcriptome tool to perform a systematic evaluation of hepatic mRNA transcripts changes in high-fat diet (HFD)-fed animals and high-fat diet with L. plantarum (HFLPD)-fed animals. HFD causes fatty liver diseases in animals, as evidenced by an increase in TG content in liver tissues compared to control animals. Based on transcriptome data, 145 differentially expressed genes (DEGs) were identified in the liver of HFD-fed mice compared to control mice. Moreover, 61 genes were differentially expressed in the liver of mice fed the HFLPD compared to mice fed the HFD. Additionally, 43 common DEGs were identified between HFD and HFLPD. These genes were enriched in metabolic processes, retinol metabolism, the PPAR signaling pathway, fatty acid degradation, arachidonic metabolism, and steroid hormone synthesis. Taking these data into consideration, it can be concluded that L. plantarum-KCC48 treatment significantly regulates the expression of genes involved in hepatosteatosis caused by HFD, which may prevent fatty liver disease.

The circadian clock has roles in mesenchymal stem cell fate decision

The circadian clock refers to the intrinsic biological rhythms of physiological functions and behaviours. It synergises with the solar cycle and has profound effects on normal metabolism and organismal fitness. Recent studies have suggested that the circadian clock exerts great influence on the differentiation of stem cells. Here, we focus on the close relationship between the circadian clock and mesenchymal stem cell fate decisions in the skeletal system. The underlying mechanisms include hormone signals and the activation and repression of different transcription factors under circadian regulation. Additionally, the clock interacts with epigenetic modifiers and non-coding RNAs and is even involved in chromatin remodelling. Although the specificity and safety of circadian therapy need to be further studied, the circadian regulation of stem cells can be regarded as a promising candidate for health improvement and disease prevention.

An evaluation of maternal serum dynamic thiol-disulfide homeostasis and ischemia modified albumin changes in pregnant women with COVID-19

Objective:

It is thought that oxidative stress, free radicals, reactive oxygen species and reactive nitrogen species affect the pathophysiology of coronavirus disease-2019 (COVID-19). This study aimed to evaluate the oxidative status in pregnant patients with COVID-19 infection according to the changes seen in the levels of maternal serum thiol-disulfide and ischemia-modified albumin (IMA).

Materials and Methods:

A study group was formed of 40 pregnant women with confirmed COVID-19 infection (study group) and a control group of 40 healthy pregnant women with no risk factors determined. In this prospective, case-controlled study, analyses were made of the maternal serum native thiol, total thiol, disulfide, IMA, and disulfide/native thiol concentrations.

Results:

The maternal serum native thiol and total thiol concentrations in the study group were determined to be statistically significantly lower (p=0.007 and p=0.006, respectively), and the disulfide/native thiol ratio was higher but not to a level of statistical significance (p=0.473). There was no difference between the two groups regarding IMA levels (p=0.731).

Conclusion:

The thiol-disulfide balance was seen to shift in the oxidant direction in pregnancies with COVID-19, which might support the view that ischemic processes play a role in the etiopathogenesis of this novel disease.

Diurnal rhythms and obesity

PURPOSE OF REVIEW

This review will discuss the recent studies that implicate disturbed diurnal rhythms with the development of obesity. The second part of the review will discuss studies that use feeding time to restore diurnal rhythms and rescue obesity.

RECENT FINDINGS

Studies in patients with obesity and diabetes reveal attenuated circadian and metabolic rhythms in adipose tissue. The use of animal models furthers our mechanistic insight on how environmental disturbances such as high-fat diet and shift work disturb circadian and metabolic rhythms. Studies in both animals and humans describe how disturbance of diurnal rhythms can lead to increased adiposity and obesity. The effects of time-restricted feeding in animals and the time of feeding in humans provide new evidence on how restoring diurnal rhythms can reverse adiposity and obesity.

SUMMARY

Many more studies in humans were performed in recent years to confirm a number of findings from animal studies. It is becoming apparent that the time of feeding and maintaining a healthy daily schedule is important for metabolic health. Ongoing studies may soon improve current recommendations regarding the time of eating and time of day behavior.

Different expressions of clock genes in fatty liver induced by high-sucrose and high-fat diets

Sucrose consumption can cause obesity and nonalcoholic fatty liver disease (NAFLD). NAFLD is associated with the disruption of circadian rhythms. We compared the alterations in NAFLD circadian rhythms induced by a high-sucrose diet (HSD) with those induced by a high-fat diet (HFD) in mice. After 8 weeks of feeding, the liver triglyceride level was increased by HSD feeding and by HFD feeding. In the liver of HSD-fed mice, the amplitude of Rorγ and the mesor (time series 24 h mean value based on the distribution of values across the cycle of the circadian rhythm) of Rorγ and Per2 were increased in comparison to those of control-diet fed mice. Compared with the HFD-fed mice, the HSD-fed mice showed increased circadian amplitude of variation in Rorγ, Per2, Cry1, and Cry2 and mesors of Rorγ, Per2, and Cry1 in the liver. Rorγ appeared to play critical roles in the entrainment of HSD into the liver circadian system, and the increased expressions of Crys and Per2 might disrupt circadian rhythms. Thus, disruption of circadian rhythms by HSD and HFD may accelerate the accumulation of liver lipid through different mechanisms.

Circadian transcription factor Dbp promotes rat calvarial osteoprogenitors osteogenic differentiation through Kiss1/GnRH/E2 signaling pathway loop

To determine the mechanism by which D-site-binding protein (Dbp) regulates rat calvarial osteoprogenitors (OPCs) osteogenic differentiation. α-Smooth muscle actin (α-SMA) + rat calvarial OPCs were extracted and purified using immunomagnetic beads. Cells were transduced with Dbp-lentivirus and divided into Dbp knockdown, Dbp overexpression and vehicle groups. After osteogenic induction for 21 days, Alizarin red staining and alkaline phosphatase (ALP) activity were examined. Expression levels of Runx2, Ocn, Osterix, Bmp4, Kiss1, and GnRH were determined using a quantitative real-time polymerase chain reaction. The observed changes in Kisspeptin, GnRH, ERα, and Runx2 were further validated via Western blot analysis. Furthermore, E2 and GnRH secretion levels were detected via an enzyme-linked immunosorbent assay (ELISA). Chromatin immunoprecipitation (ChIP) and luciferase assay were used to assess the effects of Dbp on the Kiss1 gene promoter. The coexpression of Dbp and Kisspeptin or GnRH was also evaluated via immunofluorescence. Following osteogenic induction, Dbp overexpression significantly increased calcium nodule formation and ALP activity, as well as Runx2, Ocn, Osterix, Bmp4, Kiss1, and GnRH messenger RNA expression, while Dbp knockdown presented the opposite results. Western blot analysis and ELISA results showed that Dbp significantly promotes Runx2, E2/ERα, Kisspeptin, and GnRH expression. These findings were confirmed by the ChIP assay, which indicated that the estrogen receptor promotes Kisspeptin expression after binding to the Kiss1 gene promoter, which is regulated by Dbp. Immunofluorescence assay showed that Dbp coexpression with Kisspeptin or GnRH varied depending on Dbp expression levels. Collectively, the circadian transcription factor Dbp promotes α-SMA + rat calvarial OPCs osteoblastic differentiation through Kiss1/GnRH/E2 signaling pathway loop.

Expression of clock gene Dbp in omental and mesenteric adipose tissue in patients with type 2 diabetes

INTRODUCTION

We previously reported in ob/ob mice, one of animal models of human type 2 diabetes mellitus (DM2), that (i) acetylation of histone H3 lysine 9 (H3K9) at the promoter region of clock gene Dbp and DBP mRNA expression are reduced in epididymal adipose tissue, (ii) binding of DBP to the promoter region of peroxisome proliferator-activated receptor (Ppar)-γ and mRNA expression of PPAR-γ1sv were decreased in preadipocytes and (iii) adiponectin secretion was decreased, leading to the impaired insulin sensitivity.

RESEARCH DESIGN AND METHODS

The present study was undertaken to evaluate whether such the changes in visceral adipose tissue were detected in patients with DM2. We obtained omental and mesenteric adipose tissue during surgery of lymph node dissection for gastric and colorectal cancers, and investigated these variables in adipose tissue (omental from gastric cancer; 13 non-DM, 12 DM2: mesenteric from colorectal cancer; 12 non-DM, 11 DM2).

RESULTS

Acetylation of histone H3K9 at the promoter region of Dbp and DBP mRNA expression in omental, but not in mesenteric adipose tissue were significantly lower in DM2 than in patients without DM. PPAR-γ mRNA expression in omental adipose tissue was also lower in patients with DM2, but not in mesenteric adipose tissue.

CONCLUSIONS

The changes in DBP-PPAR-γ axis observed in mice with diabetes were also detected in patients with DM2. Because adiponectin secretion is reported to be enhanced through the PPAR-γ-related mechanism, this study supports the hypothesis that omental adipose tissue is involved in the mechanism of DM2.

Influence of obesity, weight loss, and free fatty acids on skeletal muscle clock gene expression

The molecular circadian clock plays a role in metabolic homeostasis. We tested the hypothesis obesity and systemic factors associated with insulin resistance affect skeletal muscle clock gene expression. We determined clock gene expression in skeletal muscle of obese women (n = 5) and men (n = 18) before and 6 mo after Roux-en-Y gastric bypass (RYGB) surgery and normal-weight controls (women n = 6, men n = 8). Skeletal muscle clock gene expression was affected by obesity and weight loss. CRY1 mRNA (P = 0.05) was increased and DBP mRNA (P < 0.05) was decreased in obese vs. normal weight women and restored to control levels after RYGB-induced weight loss. CLOCK, CRY1, CRY2, and DBP mRNA (P < 0.05) was decreased in obese men compared with normal weight men. Expression of all other clock genes was unaltered by obesity or weight loss in both cohorts. We correlated clock gene expression with clinical characteristics of the participants. Among the genes studied, DBP and PER3 expression was inversely correlated with plasma lipids in both cohorts. Circadian time-course studies revealed that core clock genes oscillate over time (P < 0.05), with BMAL1, CIART, CRY2, DBP, PER1, and PER3 expression profiles altered by palmitate treatment. In conclusion, skeletal muscle clock gene expression and function is altered by obesity, coincident with changes in plasma lipid levels. Palmitate exposure disrupts clock gene expression in myotubes, indicating that dyslipidemia directly alters the circadian program. Strategies to reduce lipid overload and prevent elevations in nonesterified fatty acid and cholesterol levels may sustain circadian clock signals in skeletal muscle.