FAT/CD36 regulates PEPCK expression in adipose tissue

Approaches to Measuring the Activity of Major Lipolytic and Lipogenic Enzymes In Vitro and Ex Vivo

Since the 1950s, one of the goals of adipose tissue research has been to determine lipolytic and lipogenic activity as the primary metabolic pathways affecting adipocyte health and size and thus representing potential therapeutic targets for the treatment of obesity and associated diseases. Nowadays, there is a relatively large number of methods to measure the activity of these pathways and involved enzymes, but their applicability to different biological samples is variable. Here, we review the characteristics of mean lipogenic and lipolytic enzymes, their inhibitors, and available methodologies for assessing their activity, and comment on the advantages and disadvantages of these methodologies and their applicability in vivo, ex vivo, and in vitro, i.e., in cells, organs and their respective extracts, with the emphasis on adipocytes and adipose tissue.

The role of CD36-Fabp4-PPARγ in skeletal muscle involves insulin resistance in intrauterine growth retardation mice with catch-up growth

BACKGROUND

Studies have shown that the high incidence of type 2 diabetes in China is associated with low birth weight and excessive nutrition in adulthood, which occurred during the famine years of the 1950s and 1960s, though the specific molecular mechanisms are unclear. In this study, we proposed a severe maternal caloric restriction during late pregnancy, followed by a post weaning high-fat diet in mice. After weaning, normal and high-fat diets were provided to mice to simulate the dietary pattern of modern society.

METHODS

The pregnant mice were divided into two groups: normal birth weight (NBW) group and low birth weight (LBW) group. After 3 weeks for weaning, the male offspring mice in the NBW and LBW groups were then randomly divided into four subgroups: NC, NH, LC and LC groups. The offspring mice in the NC, NH, LC and LC groups were respectively fed with normal diet, normal diet, high-fat diet and high-fat diet for 18 weeks. After 18 weeks of dietary intervention, detailed analyses of mRNA and protein expression patterns, signaling pathway activities, and promoter methylation states were conducted for all relevant genes.

RESULTS

After dietary intervention for 18 weeks, the expressions of CD36, Fabp4, PPARγ, FAS, and ACC1 in the skeletal muscle tissue of the LH group were significantly increased compared with the LC and NH groups (P < 0.05). The level of p-AMPK/AMPK in the skeletal muscle tissue of the LH group was significantly decreased compared with the LC and NH groups (P < 0.05). CPT1 and PGC-1α protein expressions were up-regulated in the LH group (P < 0.05) compared to the LC group. Additionally, the DNA methylation levels of the PGC-1α and GLUT4 gene promoters in the skeletal muscle of the LH groups were higher than those of the LC and NH groups (P < 0.05). However, PPARγ DNA methylation level in the LH group was lower than those of the LC and NH groups (P < 0.05).

CONCLUSIONS

LBW combined with high-fat diets may increase insulin resistance and diabetes through regulating the CD36-related Fabp4-PPARγ and AMPK/ACC signaling pathways.

Salvia hispanica L. (chia) seed promotes body fat depletion and modulates adipocyte lipid handling in sucrose-rich diet-fed rats

The aim of this study was to analyze the effects of Salvia hispanica L. (chia) seed upon metabolic pathways that play a key role in adipose tissue lipid handling which could be involved in visceral adiposity reduction developed in rats fed a sucrose-rich diet (SRD). Male Wistar rats were fed with a reference diet (RD) -6 months- or SRD-3 months. Then, the last group was randomly divided into two subgroups. One subgroup continued receiving the SRD up to 6 months and the other was fed with a SRD where whole chia seed was incorporated as the source of dietary fat for the next 3 months (SRD + CHIA). Results showed that chia seed in the SRD-fed rat reduced the abdominal and thoracic circumferences, carcass fat content, adipose tissue weights, and visceral adiposity index. This was accompanied by an improvement in insulin sensitivity and plasma lipid profile. In epididymal adipose tissue, the decreased fat cell triglyceride content was associated with a reduction in both, FAT/CD 36 plasma membrane levels and the fat synthesis enzyme activities. There were not changes in oxidative CPT enzyme activities. PKCβ and the precursor and mature forms of SREBP-1 protein levels were decreased, while pAMPK was increased. Our findings suggest that chia seed supplementation can modulate essential pathways of lipid metabolism in adipose tissue, contributing to reduced visceral fat accumulation in SRD-fed rats.

Emodin Improves Glucose and Lipid Metabolism Disorders in Obese Mice via Activating Brown Adipose Tissue and Inducing Browning of White Adipose Tissue

BACKGROUND

Adipose tissue (e.g. white, brown and brite) plays a critical role in modulating energy metabolism. Activating brown adipose tissue (BAT) and inducing browning in white adipose tissue (WAT) has been proposed to be a potential molecular target for obesity treatment. Emodin is a natural anthraquinone derivative that exhibits variety of pharmacologic effects including lowering lipids and regulating glucose utilization. However, the underlying mechanism of action is still unclear. In the present study, we investigated whether emodin could alleviate obesity via promoting browning process in adipose tissue.

METHODS

C57BL/6J mice were fed with high fat diet to induce obesity. Emodin at the doses of 40 and 80 mg/kg were orally given to obesity mice for consecutive 6 weeks. Parameters including fasting blood glucose, oral glucose tolerance, blood lipids, and the ratios of subcutaneous white adipose tissue (scWAT) or BAT mass to body weight, and morphology of adipose tissue were observed. Besides, the protein expression of uncoupling protein 1 (UCP1) and prohibitin in BAT and scWAT was determined by immunohistochemistry method. Relative mRNA expression of Cd137, transmembrane protein 26 (Tmem26) and Tbx1 in scWAT was analyzed using qRT-PCR. And the protein expression of UCP1, CD36, fatty acid transporter 4 (FATP4), peroxisome proliferator-activated receptor alpha (PPARα) and prohibitin of scWAT and BAT were analyzed using western blotting. In addition, ultra-high-performance liquid chromatography with electrospray ionization tandem mass spectrometry was utilized to detect the small lipid metabolites of scWAT and BAT.

RESULTS

Emodin decreased the body weight and food intake in HFD-induced obesity mice, and it also improved the glucose tolerance and reduced the blood lipids. Emodin treatment induced beiging of WAT, and more multilocular lipid droplets were found in scWAT. Also, emodin significantly increased markers of beige adipocytes, e.g. Cd137, Tmem26 and Tbx1 mRNA in scWAT, and UCP1, CD36, FATP4, PPARα and prohibitin protein expression in scWAT and BAT. Furthermore, emodin perturbed the lipidomic profiles in scWAT and BAT of obese mice. Emodin increased total ceramides (Cers), lysophosphatidylcholines (LPCs), lyso-phosphatidylcholines oxygen (LPCs-O), and phosphatidylethanolamines oxygen (PEs-O) species concentration in scWAT. Specifically, emodin significantly up-regulated levels of Cer (34:1), LPC (18:2), LPC-(O-20:2), PC (O-40:7), PE (O-36:3), PE (O-38:6), PE (O-40:6), and sphingolipid (41:0) [SM (41:0)], and down-regulated PC (O-38:0), PE (O-40:4), PE (O-40:5) in scWAT of obesity mice. In terms of lipid matabolites of BAT, the emodin remarkably increased the total PCs levels, which was driven by significant increase of PC (30:0), PC (32:1), PC (32:2), PC (33:4) and PC (38:0) species. In addition, it also increased species of LPCs, e.g. LPC (20:0), LPC (20:1), LPC (22:0), LPC (22:1), LPC (24:0), and LPC (24:1). Especially, emodin treatment could reverse the ratio of PC/PE in HFD-induced obese mice.

CONCLUSIONS

These results indicated that emodin could ameliorate adiposity and improve metabolic disorders in obese mice. Also, emodin could promote browning in scWAT and activate the BAT activities. In addition, emodin treatment-induced changes to the scWAT and BAT lipidome were highly specific to certain molecular lipid species, indicating that changes in tissue lipid content reflects selective remodeling in scWAT and BAT of both glycerophospholipids and sphingolipids in response to emodin treatment.

The Multifunctionality of CD36 in Diabetes Mellitus and Its Complications-Update in Pathogenesis, Treatment and Monitoring

CD36 is a multiligand receptor contributing to glucose and lipid metabolism, immune response, inflammation, thrombosis, and fibrosis. A wide range of tissue expression includes cells sensitive to metabolic abnormalities associated with metabolic syndrome and diabetes mellitus (DM), such as monocytes and macrophages, epithelial cells, adipocytes, hepatocytes, skeletal and cardiac myocytes, pancreatic β-cells, kidney glomeruli and tubules cells, pericytes and pigment epithelium cells of the retina, and Schwann cells. These features make CD36 an important component of the pathogenesis of DM and its complications, but also a promising target in the treatment of these disorders. The detrimental effects of CD36 signaling are mediated by the uptake of fatty acids and modified lipoproteins, deposition of lipids and their lipotoxicity, alterations in insulin response and the utilization of energy substrates, oxidative stress, inflammation, apoptosis, and fibrosis leading to the progressive, often irreversible organ dysfunction. This review summarizes the extensive knowledge of the contribution of CD36 to DM and its complications, including nephropathy, retinopathy, peripheral neuropathy, and cardiomyopathy.

Intricate Regulation of Phosphoenolpyruvate Carboxykinase (PEPCK) Isoforms in Normal Physiology and Disease

BACKGROUND

The phosphoenolpyruvate carboxykinase (PEPCK) isoforms are considered as rate-limiting enzymes for gluconeogenesis and glyceroneogenesis pathways. PEPCK exhibits several interesting features such as a) organelle-specific isoforms (cytosolic and a mitochondrial) in vertebrate clade, b) tissue-specific expression of isoforms and c) organism-specific requirement of ATP or GTP as a cofactor. In higher organisms, PEPCK isoforms are intricately regulated and activated through several physiological and pathological stimuli such as corticoids, hormones, nutrient starvation and hypoxia. Isoform-specific transcriptional/translational regulation and their interplay in maintaining glucose homeostasis remain to be fully understood. Mounting evidence indicates the significant involvement of PEPCK isoforms in physiological processes (development and longevity) and in the progression of a variety of diseases (metabolic disorders, cancer, Smith-Magenis syndrome).

OBJECTIVE

The present systematic review aimed to assimilate existing knowledge of transcriptional and translational regulation of PEPCK isoforms derived from cell, animal and clinical models.

CONCLUSION

Based on current knowledge and extensive bioinformatics analysis, in this review we have provided a comparative (epi)genetic understanding of PCK1 and PCK2 genes encompassing regulatory elements, disease-associated polymorphisms, copy number variations, regulatory miRNAs and CpG densities. We have also discussed various exogenous and endogenous modulators of PEPCK isoforms and their signaling mechanisms. A comprehensive review of existing knowledge of PEPCK regulation and function may enable identification of the underlying gaps to design new pharmacological strategies and interventions for the diseases associated with gluconeogenesis.

The PPARδ Agonist GW501516 Improves Lipolytic/Lipogenic Balance through CPT1 and PEPCK during the Development of Pre-Implantation Bovine Embryos

The PPARs (peroxisome proliferator-activated receptors) play critical roles in the regulation of lipid and glucose metabolism. PPARδ, a member of the PPARs family, is associated with decreased susceptibility to ectopic lipid deposition and is implicated in the regulation of mitochondrial processes. The current study aimed to determine the role of PPARδ in fatty acid β-oxidation and its influence on PEPCK for the lipogenic/lipolytic balance during in vitro bovine oocyte maturation and embryo development. Activation of PPARδ by GW501516, but not 2-BP, was indicated by intact embryonic PEPCK (cytosolic) and CPT1 expression and the balance between free fatty acids and mitochondrial β-oxidation that reduced ROS and inhibited p-NF-κB nuclear localization. Genes involved in lipolysis, fatty acid oxidation, and apoptosis showed significant differences after the GW501516 treatment relative to the control- and 2-BP-treated embryos. GSK3787 reversed the PPARδ-induced effects by reducing PEPCK and CPT1 expression and the mitochondrial membrane potential, revealing the importance of PPARδ/PEPCK and PPARδ/CPT1 for controlling lipolysis during embryo development. In conclusion, GW501516-activated PPARδ maintained the correlation between lipolysis and lipogenesis by enhancing PEPCK and CPT1 to improve bovine embryo quality.

PEPCK1 Antisense Oligonucleotide Prevents Adiposity and Impairs Hepatic Glycogen Synthesis in High-Fat Male Fed Rats

The increased hepatic gluconeogenesis in type 2 diabetes mellitus has often been ascribed to increased transcription of phosphoenolpyruvate carboxykinase 1, cystolic form (PEPCK1), although recent evidence has questioned this attribution. To assess the metabolic role of PEPCK1, we treated regular chow fed and high-fat fed (HFF) male Sprague-Dawley rats with a 2'-O-methoxyethyl chimeric antisense oligonucleotide (ASO) against PEPCK1 and compared them with control ASO-treated rats. PEPCK1 ASO effectively decreased PEPCK1 expression in the liver and white adipose tissue. In chow fed rats, PEPCK1 ASO did not alter adiposity, plasma glucose, or insulin. In contrast, PEPCK1 ASO decreased the white adipose tissue mass in HFF rats but without altering basal rates of lipolysis, de novo lipogenesis, or glyceroneogenesis in vivo. Despite the protection from adiposity, hepatic insulin sensitivity was impaired in HFF PEPCK1 ASO-treated rats. PEPCK1 ASO worsened hepatic steatosis, although without additional impairments in hepatic insulin signaling or activation of inflammatory signals in the liver. Instead, the development of hepatic insulin resistance and the decrease in hepatic glycogen synthesis during a hyperglycemic clamp was attributed to a decrease in hepatic glucokinase (GCK) expression and decreased synthesis of glycogen via the direct pathway. The decrease in GCK expression was associated with increased expression of activating transcription factor 3, a negative regulator of GCK transcription. These studies have demonstrated that PEPCK1 is integral to coordinating cellular metabolism in the liver and adipose tissue, although it does not directly effect hepatic glucose production or adipose glyceroneogenesis.

Molecular adaptations in human subcutaneous adipose tissue after ten weeks of endurance exercise training in healthy males

Endurance exercise training induces adaptations in metabolically active organs, but adaptations in human subcutaneous adipose tissue (scAT) remains incompletely understood. On the basis of animal studies, we hypothesized that endurance exercise training would increase the expression of proteins involved in lipolysis and glucose uptake in scAT. To test these hypotheses, 19 young and healthy males were randomized to either endurance exercise training (TR; age 18-24 yr; BMI 19.0-25.4 kg/m²) or a nonexercising control group (CON; age 21-35 yr; BMI 20.5-28.8 kg/m²). Abdominal subcutaneous fat biopsies and blood were obtained at rest before and after intervention. By using Western blotting and PCR, we determined expression of lipid droplet-associated proteins, various proteins involved in substrate metabolism, and mRNA abundance of cell surface G protein-coupled receptors (GPCRs). Adipose tissue insulin sensitivity was determined from fasting plasma insulin and nonesterified fatty acids (adipose tissue insulin resistance index; Adipo-IR). Adipo-IR improved in TR compared with CON ( P = 0.03). This was accompanied by increased insulin receptor (IR) protein expression in scAT with a 1.54-fold (SD 0.79) change from baseline in TR vs. 0.85 (SD 0.30) in CON ( P = 0.007). Additionally, hexokinase II (HKII) and succinate dehydrogenase complex subunit A (SDHA) protein increased in TR compared with CON ( P = 0.006 and P = 0.04, respectively). We did not observe changes in lipid droplet-associated proteins or mRNA abundance of GPCRs. Collectively, 10 weeks of endurance exercise training improved adipose tissue insulin sensitivity, which was accompanied by increased IR, HKII, and SDHA protein expression in scAT. We suggest that these adaptations contribute to an improved metabolic flexibility. NEW & NOTEWORTHY This study is the first to investigate the molecular adaptations in human subcutaneous adipose tissue (scAT) after endurance exercise training compared with a nonexercising control group. We show that endurance exercise training improves insulin sensitivity in human scAT, and this is accompanied by increased expression of insulin receptor, hexokinase II, and succinate dehydrogenase complex subunit A. Collectively, our data suggest that endurance exercise training induces molecular adaptations in human scAT, which may contribute to an improved metabolic flexibility.

Mild Methylenetetrahydrofolate Reductase Deficiency Alters Inflammatory and Lipid Pathways in Liver

SCOPE

Dietary and genetic folate disturbances can lead to nonalcoholic fatty liver disease (NAFLD). A common variant in methylenetetrahydrofolate reductase (MTHFR 677C→T) causes mild MTHFR deficiency with lower 5-methyltetrahydrofolate for methylation reactions. The goal is to determine whether mild murine MTHFR deficiency contributes to NAFLD-related effects.

METHODS AND RESULTS

Wild-type and Mthfr^+/- mice, a model for the human variant, are fed control (CD) or high-fat (HFAT) diets for 8 weeks. On both diets, MTHFR deficiency results in decreased S-adenosylmethionine, increased S-adenosylhomocysteine, and decreased betaine with reduced methylation capacity, and changes in expression of several inflammatory or anti-inflammatory mediators (Saa1, Apoa1, and Pon1). On CD, MTHFR deficiency leads to microvesicular steatosis with expression changes in lipid regulators Xbp1s and Cyp7a1. The combination of MTHFR deficiency and HFAT exacerbates changes in inflammatory mediators and introduces additional effects on inflammation (Saa2) and lipid metabolism (Nr1h4, Srebf1c, Ppara, and Crot). These effects are consistent with increased expression of pro-inflammatory HDL precursors and greater lipid accumulation. MTHFR deficiency may enhance liver injury through alterations in methylation capacity, inflammatory response, and lipid metabolism.

CONCLUSION

Individuals with the MTHFR variant may be at increased risk for liver disease and related complications, particularly when consuming high-fat diets.

Involvement of glucocorticoid prereceptor metabolism and signaling in rat visceral adipose tissue lipid metabolism after chronic stress combined with high-fructose diet

Both fructose overconsumption and increased glucocorticoids secondary to chronic stress may contribute to overall dyslipidemia. In this study we specifically assessed the effects and interactions of dietary fructose and chronic stress on lipid metabolism in the visceral adipose tissue (VAT) of male Wistar rats. We analyzed the effects of 9-week 20% high fructose diet and 4-week chronic unpredictable stress, separately and in combination, on VAT histology, glucocorticoid prereceptor metabolism, glucocorticoid receptor subcellular redistribution and expression of major metabolic genes. Blood triglycerides and fatty acid composition were also measured to assess hepatic Δ9 desaturase activity. The results showed that fructose diet increased blood triglycerides and Δ9 desaturase activity. On the other hand, stress led to corticosterone elevation, glucocorticoid receptor activation and decrease in adipocyte size, while phosphoenolpyruvate carboxykinase, adipose tissue triglyceride lipase, FAT/CD36 and sterol regulatory element binding protein-1c (SREBP-1c) were increased, pointing to VAT lipolysis and glyceroneogenesis. The combination of stress and fructose diet was associated with marked stimulation of fatty acid synthase and acetyl-CoA carboxylase mRNA level and with increased 11β-hydroxysteroid dehydrogenase type 1 and hexose-6-phosphate dehydrogenase protein levels, suggesting a coordinated increase in hexose monophosphate shunt and de novo lipogenesis. It however did not influence the level of peroxisome proliferator-activated receptor-gamma, SREBP-1c and carbohydrate responsive element-binding protein. In conclusion, our results showed that only combination of dietary fructose and stress increase glucocorticoid prereceptor metabolism and stimulates lipogenic enzyme expression suggesting that interaction between stress and fructose may be instrumental in promoting VAT expansion and dysfunction.

Compromised mechanical homeostasis in arterial aging and associated cardiovascular consequences

Aging leads to central artery stiffening and associated hemodynamic sequelae. Because healthy arteries exhibit differential geometry, composition, and mechanical behaviors along the central vasculature, we sought to determine whether wall structure and mechanical function differ across five vascular regions-the ascending and descending thoracic aorta, suprarenal and infrarenal abdominal aorta, and common carotid artery-in 20 versus 100-week-old male wild-type mice. Notwithstanding generally consistent changes across these regions, including a marked thickening of the arterial wall, diminished in vivo axial stretch, and loss of elastic energy storage capacity, the degree of changes tended to be slightly greater in abdominal than in thoracic or carotid vessels. Likely due to the long half-life of vascular elastin, most mechanical changes in the arterial wall resulted largely from a distributed increase in collagen, including thicker fibers in the media, and localized increases in glycosaminoglycans. Changes within the central arteries associated with significant increases in central pulse pressure and adverse changes in the left ventricle, including increased cardiac mass and decreased diastolic function. Given the similar half-life of vascular elastin in mice and humans but very different life-spans, there are important differences in the aging of central vessels across these species. Nevertheless, the common finding of aberrant matrix remodeling contributing to a compromised mechanical homeostasis suggests that studies of central artery aging in the mouse can provide insight into mechanisms and treatment strategies for the many adverse effects of vascular aging in humans.

Rosiglitazone is superior to resveratrol in inducing the expression of glyceroneogenic genes in adipose tissue from obese participants

We compared the effects of resveratrol and rosiglitazone, alone and in combination, on indices of fatty acid re-esterification in cultured adipose tissue from obese participants (n = 17) undergoing gastric bypass. Rosiglitazone induced PDK4 and PEPCK gene expression to a greater extent than resveratrol. Co-treatment with both compounds induced PDK4 and PEPCK expression in parallel with reductions in the fatty acid to glycerol ratio. Our findings suggest beneficial effects of resveratrol and rosiglitazone co-treatment.

Proteomics Analysis Reveals an Important Role for the PPAR Signaling Pathway in DBDCT-Induced Hepatotoxicity Mechanisms

A patented organotin di-n-butyl-di-(4-chlorobenzohydroxamato)tin (DBDCT) with high a antitumor activity was designed, however, its antitumor and toxic mechanisms have not yet been clearly illustrated. Hepatic proteins of DBDCT-treated rats were identified and analyzed using LC-MS/MS with label-free quantitative technology. In total, 149 differentially expressed proteins were successfully identified. Five protein and mRNA expressions were involved in the peroxisome proliferator-activated receptor (PPAR) signaling pathway, including a scavenger receptor (CD36), adipocyte fatty acid binding protein 4 (FABP4), enoyl-CoA hydratase (EHHADH), acetyl-CoA acyltransferase 1 (ACAA1), and phosphoenolpyruvate carboxykinase (PEPCK) in DBDCT-treated Rat Liver (BRL) cells. PPAR-α and PPAR-λ were also significantly decreased at both protein and mRNA levels. Furthermore, compared with the DBDCT treatment group, a special blocking agent of PPAR-λ T0070907 was used to evaluate the relationship between PPAR-λ and its downstream genes. Our studies indicated that DBDCT may serve as a modulator of PPAR-λ, further up-regulating CD36, FABP4 and EHHADH on the PPAR signal pathway.

Cycling our way to fit fat

Adipose tissue is increasingly being recognized as a key regulator of whole body carbohydrate and lipid metabolism. In conditions of obesity and insulin resistance mitochondrial content in this tissue is reduced, while treatment with insulin sensitizing drugs such as thiazolidinediones (TZDs) increase mitochondrial content. It has been known for decades that exercise increases mitochondrial content in skeletal muscle and now several laboratories have shown similar effects in adipose tissue. To date the specific mechanisms mediating this effect have not been fully identified. In this review we highlight recent work suggesting that increases in lipolysis and subsequently fatty acid re‐esterification trigger the activation of 5' AMP‐activated protein kinase (AMP) activated protein kinase and ultimately the induction of mitochondrial biogenesis. It is our current view that this pathway could be a unifying mechanism linking numerous systemic factors (catecholamines, interleukin‐6, meteorin‐like) to induction of mitochondrial biogenesis following exercise.

Effects of vitamin D and resveratrol on metabolic associated markers in liver and adipose tissue from SAMP8 mice

SAMP8 mice exhibit multiple metabolic characteristics associated with age, and it is a suitable candidate for researching aging associated metabolic dysfunction.

OBJECTIVES

We aimed to 1) explore how key metabolic markers will be altered in both liver and adipose tissue with aging in SAMP8 mice; and 2) how the combination of vitamin D (VD) with resveratrol (RSV) will affect aging associated metabolic impairment in liver and adipose tissue from SAMP8 mice.

METHODS

SAMP8 mice and their control SAMR1 mice were divided into 5 groups, i.e. SAMR1, SAMP8, SAMP8 mice supplemented with VD, RSV and VD combined with RSV group, respectively. At the end of the intervention, glucose and insulin tolerance, p-AMP-activated protein kinase (AMPK) and amyloid precursor protein (APP), and endoplasmic reticulum (ER) stress markers in liver and adipose tissue, adiponectin secretion, p-NF-κBp65 and TNF-α protein expression in adipose tissue were determined.

RESULTS

Compared to SAMR1 control, SAMP8 mice demonstrate impaired glucose tolerance and reduction in circulating adiponectin level; in the liver, SAMP8 mice have reduction in p-Aktser473, elevation in PTP1B and APP, p-eIF2α, GRP78 and p-JNK protein expression. In epididymal (EPI) fat, SAMP8 mice also have elevated p-Aktser473 and PTP1B compared to SAMR1 mice. In both epididymal (EPI) and subcutaneous (SC) fat, there were elevated ER stress markers, reduced p-AMPK and elevated APP, as well as elevated p-NF-κBp65 and TNF-α protein expression from SAMP8 compared to SAMR1 mice. In liver, the combined intervention significantly restored p-Aktser473, p-eIF2α and p-JNK protein expression. In both EPI and SC fat, the combined intervention is effective for reducing p-NF-κB p65 and TNF-α in both fat depot, while only partially reduced ER stress markers in SC fat. As for adiponectin, their combination is unable to reverse reduction in adiponectin level. Adiponectin secretion in SC fat from VD, RSV and VDRSV group were also significantly reduced compared to SAMR1.

CONCLUSION

The combined intervention might exert greater beneficial effects for reversing aging associated metabolic dysfunction in liver and adipose tissue from SAMP8 mice.

Differential modulation of cytosolic lipases activities in liver and adipose tissue by high-carbohydrate diets

Several studies have demonstrated that a high-fructose (FRUC) diet induces metabolic and haemodynamic abnormalities, known as the metabolic syndrome, which are characterised by obesity, glucose intolerance, insulin resistance, dyslipidaemia and hypertension. In this study, the effect of a FRUC diet (60 % fructose) for 8 weeks on the metabolism of lipids in liver and epididymal adipose tissue from Wistar rats was compared with the AIN-93M diet and the effects of the AIN-93M diet were compared with a chow diet. The FRUC diet induced marked increases in both hepatocyte lipid droplet volume and postprandial serum levels of triacylglycerol (TAG), but reduced the postprandial serum levels of insulin. The AIN-93M diet induced marked increases in the hepatocyte lipid droplet volume and the serum levels of insulin, without affecting the serum levels of TAG. We found that isocaloric substitution of cornstarch, dextrinised cornstarch and sucrose (AIN-93M diet) for fructose did not affect the hepatic VLDL-TAG secretion and adipose tissue glucose uptake, lipolysis and cytosolic lipases activities in rats. However, the high-fructose diet induced a severe steatosis in liver accompanied by a decrease in cytosolic lipases activities. In adipose tissue, the FRUC diet induced a decrease in the lipoprotein lipase activity, and an increase in lipogenesis. FRUC and AIN-93M diets induced changes in lipid homeostasis in liver and adipose tissue by distinct biochemical mechanisms.

MALDI Mass Spectrometry Imaging of Lipids and Gene Expression Reveals Differences in Fatty Acid Metabolism between Follicular Compartments in Porcine Ovaries

In mammals, oocytes develop inside the ovarian follicles; this process is strongly supported by the surrounding follicular environment consisting of cumulus, granulosa and theca cells, and follicular fluid. In the antral follicle, the final stages of oogenesis require large amounts of energy that is produced by follicular cells from substrates including glucose, amino acids and fatty acids (FAs). Since lipid metabolism plays an important role in acquiring oocyte developmental competence, the aim of this study was to investigate site-specificity of lipid metabolism in ovaries by comparing lipid profiles and expression of FA metabolism-related genes in different ovarian compartments. Using MALDI Mass Spectrometry Imaging, images of porcine ovary sections were reconstructed from lipid ion signals for the first time. Cluster analysis of ion spectra revealed differences in spatial distribution of lipid species among ovarian compartments, notably between the follicles and interstitial tissue. Inside the follicles analysis differentiated follicular fluid, granulosa, theca and the oocyte-cumulus complex. Moreover, by transcript quantification using real time PCR, we showed that expression of five key genes in FA metabolism significantly varied between somatic follicular cells (theca, granulosa and cumulus) and the oocyte. In conclusion, lipid metabolism differs between ovarian and follicular compartments.

Heat shock proteins: in vivo heat treatments reveal adipose tissue depot-specific effects

Heat treatments (HT) and the induction of heat shock proteins (HSPs) improve whole body and skeletal muscle insulin sensitivity while decreasing white adipose tissue (WAT) mass. However, HSPs in WAT have been understudied. The purpose of the present study was to examine patterns of HSP expression in WAT depots, and to examine the effects of a single in vivo HT on WAT metabolism. Male Wistar rats received HT (41°C, 20 min) or sham treatment (37°C), and 24 h later subcutaneous, epididymal, and retroperitoneal WAT depots (SCAT, eWAT, and rpWAT, respectively) were removed for ex vivo experiments and Western blotting. SCAT, eWAT, and rpWAT from a subset of rats were also cultured separately and received a single in vitro HT or sham treatment. HSP72 and HSP25 expression was greatest in more metabolically active WAT depots (i.e., eWAT and rpWAT) compared with the SCAT. Following HT, HSP72 increased in all depots with the greatest induction occurring in the SCAT. In addition, HSP25 increased in the rpWAT and eWAT, while HSP60 increased in the rpWAT only in vivo. Free fatty acid (FFA) release from WAT explants was increased following HT in the rpWAT only, and fatty acid reesterification was decreased in the rpWAT but increased in the SCAT following HT. HT increased insulin responsiveness in eWAT, but not in SCAT or rpWAT. Differences in HSP expression and induction patterns following HT further support the growing body of literature differentiating distinct WAT depots in health and disease.