Up-regulation of stearoyl-CoA desaturase 1 and elongase 6 genes expression in rat lipogenic tissues by chronic food restriction and chronic food restriction/refeeding

Gender-Dependent Effect of Progesterone on the Expression of Metallothionein Genes in Rat Inguinal Adipose Tissue

Metallothioneins (MTs) are low-molecular-weight metal-binding proteins potentially involved in the detoxification of heavy metals, protection against oxidative stress, and other biological processes. This study examined progesterone's influence on Mt gene expression in rat adipose tissue. Wistar rats (females and males) received 100 mg of progesterone per rat. MT mRNA and protein levels were quantified by real-time PCR and Western blotting methods. Using radioimmunoassay, the serum progesterone level was measured. In this study, progesterone administration to female rats led to a 2.5-fold increase in serum progesterone concentration and significant increases in MT-1, MT-2A mRNA, and protein levels in inguinal WAT (WATi), compared to untreated female rats. RU 486 (progesterone receptor antagonist) abolished progesterone's influence on Mt-1 and Mt-2A gene expression in female WATi. Progesterone administration did not alter the level of Mt-3 gene expression in WATi or Mt-1 and Mt-2A in retroperitoneal WAT or brown adipose tissue in female rats.

Two Regions with Different Expression of Lipogenic Enzymes in Rats' Posterior Subcutaneous Fat Depot

Lipid metabolism in various adipose tissue depots can differ vastly. This also applies to lipogenesis, the process of synthesizing fatty acids from acetyl-CoA. This study compared the expression of some lipogenic enzymes: fatty acid synthase (FASN), ATP-citrate lyase (ACLY), and malic enzyme 1 (ME1) in different regions of the posterior subcutaneous adipose tissue in rats. Methods and Results: Posterior subcutaneous adipose tissue collected from twelve-month-old Wistar rats was divided into six parts (A-F). The expression of genes encoding lipogenic enzymes was assessed by measuring their activity and mRNA levels using real-time PCR. In the gluteal region of the fat pad, there were much higher levels of activity and mRNA for these lipogenic enzymes compared to the dorsolumbar region. The mRNA level of FASN increased by more than twentyfold, whereas the level of ME1 and ACLY increased eight- and fivefold respectively. This phenomenon was observed in both old and young animals. Furthermore, the lack of uncoupling protein one (Ucp1) expression suggests that neither the presence of brown adipocytes in the gluteal part nor the transformation of white adipocytes into beige contributed to the observed differences. Conclusion: These results indicate that the gluteal white adipose tissue appears to be a unique and separate subcutaneous fat depot.

Transcriptional modulation of heat shock proteins and adipogenic regulators in bovine adipocytes following heat exposure

This research endeavored to elucidate the transcriptional modulation of heat shock proteins and adipogenic regulators in bovine subcutaneous adipocytes following thermal exposure. Post-differentiation, mature adipocytes were subjected to three treatments of control (CON), moderate (MHS), and extreme (EHS) heat stress. These treatments consist of thermal conditions at temperatures of 38 °C (CON), 39.5 °C (MHS), or 41 °C (EHS) along with of 3 or 12 h. There was no statistically significant variations observed in the gene expressions of HSP27 and HSP70 when comparing CON with MHS across both exposures. Contrastingly, when comparing CON with EHS, an upregulation (P < 0.01) in HSP27 gene expression was evident for both 3 and 12 h of incubation, while HSP70 gene expression exhibited elevation (P < 0.01) at the 3-h mark, with no change observed at 12 h. Protein quantification, however, revealed an elevation (P < 0.01) in HSP27 and HSP70 for both CON vs. MHS and CON vs. EHS at the 12-h exposure. This trend in protein level mirrored (P < 0.05) that of proliferator-activated receptor-gamma (PPARγ). Elevated (P < 0.05) protein levels of fatty acid synthase (FAS) were exclusively discernible in the CON vs. MHS. Increased (P < 0.01) transcriptional activity of PPARγ, CCAAT/enhancer-binding protein alpha (C/EBPα), stearoyl-CoA desaturase (SCD), and FAS was evident in the CON vs. EHS comparison. Complementary to these molecular findings, an augmented lipid droplet accumulation was observed (P < 0.01) in EHS-exposed adipocytes progressively from day 6 through day 9. Our current study highlights how different levels and lengths of heat stress can impact the activity of important heat-related proteins and factors that play a role in fat development in beef cattle. These findings can help guide strategies to manage how beef cattle are exposed to heat, which can affect fat storage and ultimately the quality of the meat's marbling.

Hepatocyte Nuclear Factor-1α Increases Fibrinogen Gene Expression in Liver and Plasma Fibrinogen Concentration in Rats with Experimental Chronic Renal Failure

Chronic kidney disease (CKD) is associated with elevated plasma fibrinogen concentration. However, the underlying molecular mechanism for elevated plasma fibrinogen concentration in CKD patients has not yet been clarified. We recently found that HNF1α was significantly upregulated in the liver of chronic renal failure (CRF) rats, an experimental model of CKD in patients. Given that the promoter region of the fibrinogen gene possesses potential binding sites for HNF1α, we hypothesized that the upregulation of HNF1α can increase fibrinogen gene expression and consequently plasma fibrinogen concentration in the experimental model of CKD. Here, we found the coordinated upregulation of Aα-chain fibrinogen and Hnfα gene expression in the liver and elevated plasma fibrinogen concentrations in CRF rats, compared with pair-fed and control animals. Liver Aα-chain fibrinogen and HNF1α mRNAs levels correlated positively with (a) liver and plasma fibrinogen levels and (b) liver HNF1α protein levels. The positive correlation between (a) liver Aα-chain fibrinogen mRNA level, (b) liver Aα-chain fibrinogen level, and (c) serum markers of renal function suggest that fibrinogen gene transcription is closely related to the progression of kidney disease. Knockdown of Hnfα in the HepG2 cell line by small interfering RNA (siRNA) led to a decrease in fibrinogen mRNA levels. Clofibrate, an anti-lipidemic drug that reduces plasma fibrinogen concentration in humans, decreased both HNF1α and Aα-chain fibrinogen mRNAs levels in (a) the liver of CRF rats and (b) HepG2 cells. The obtained results suggest that (a) an elevated level of liver HNF1α can play an important role in the upregulation of fibrinogen gene expression in the liver of CRF rats, leading to an elevated concentration of plasma fibrinogen, a protein related to the risk of cardiovascular disease in CKD patients, and (b) fibrates can decrease plasma fibrinogen concentration through inhibition of HNF1α gene expression.

Hepatocyte Nuclear Factor 1α Proinflammatory Effect Linked to the Overexpression of Liver Nuclear Factor–κB in Experimental Model of Chronic Kidney Disease

Chronic kidney disease (CKD) is associated with low-grade inflammation that activates nuclear factor–κB (NF–κB), which upregulates the expression of numerous NF–κB responsive genes, including the genes encoding IL-6, ICAM-1, VCAM-1, and MCP-1. Herein, we found the coordinated overexpression of genes encoding RelA/p65 (a subunit of NF–κB) and HNF1α in the livers of chronic renal failure (CRF) rats—an experimental model of CKD. The coordinated overexpression of RelA/p65 and HNF1α was associated with a significant increase in IL-6, ICAM-1, VCAM-1, and MCP-1 gene expressions. A positive correlation between liver RelA/p65 mRNA levels and a serum concentration of creatinine and BUN suggest that RelA/p65 gene transcription is tightly related to the progression of renal failure. The knockdown of HNF1α in the HepG2 cell line by siRNA led to a decrease in Rel A/p65 mRNA levels. This was associated with a decrease in IL-6, ICAM-1, VCAM-1, and MCP-1 gene expressions. The simultaneous repression of HNF-1α and RelA/p65 by clofibrate is tightly associated with the downregulation of IL-6, ICAM-1, VCAM-1, and MCP-1 gene expression. In conclusion, our findings suggest that NF–κB could be a downstream component of the HNF1α-initiated signaling pathway in the livers of CRF rats.

Late-Onset Calorie Restriction Improves Lipid Metabolism and Aggravates Inflammation in the Liver of Old Wistar Rats

Aging is a progressive process that could disturb metabolic homeostasis in the liver via ectopic lipid accumulation, oxidative stress, and deterioration of inflammatory response. Although calorie restriction (CR) is recognized as beneficial for life span and health span prolongation, it is still unclear how late-onset CR, characterized by late beginning and short duration, affects age-related processes. The aim of this study was to examine how late-onset CR-induced metabolic adjustments impact lipid status and inflammation in the liver of old rats. The experiments were conducted on aging male Wistar rats fed ad libitum (AL) or exposed to late-onset CR (60% of AL daily intake) from 21st to 24th month. The results showed that late-onset CR reduces body weight, visceral adipose tissue and liver mass, and triglyceride levels when compared to old animals on AL diet. The ameliorating effects of CR on lipid metabolism include increased activity of AMP-activated protein kinase, suppressed de novo fatty acid synthesis, stimulated β-oxidation, decreased lipotoxicity, and limited triglyceride synthesis and packaging in the liver. Restricted diet regime, however, does not improve expression of antioxidant enzymes, although it leads to progression of age-related inflammation in the liver, partially through lower corticosterone concentration and decreased activation of glucocorticoid receptor. In conclusion, late-onset CR is able to restore age-related imbalance of lipid metabolism in the liver, but has a negative impact on hepatic inflammatory status, implying that the type of diet for older individuals must be balanced and chosen carefully with appropriate duration and start point.

Effects of Birth Weight on Animal Performance, Fattening Traits and Meat Quality of Lambs

Simple Summary

It is accepted that a low body weight at birth (<4 kg) might impair postnatal muscle and increase adipose tissue development during the whole life of lambs. Therefore, in the present study, we aimed to evaluate the effect of body weight at birth of lambs on the growth performance, ruminal parameters, digestibility, non-carcass components, carcass traits, physicochemical characteristics and fatty acid profile of meat when slaughtered at 27 kg. Compared to the lambs born with a high weight (>5.5 kg), the lambs born with a low body weight showed a worse animal performance during the fattening period, and increased fat depots with a higher content of saturated fatty acids and a reduced tenderness of meat.

Abstract

Intrauterine growth restriction (IUGR) is a key developmental programming factor which might impair both the feed efficiency of lambs and meat quality, since it deeply impacts skeletal muscle and adipose tissue development. To determine the effect of birth weight on the growth performance, ruminal parameters, digestibility, non-carcass components, carcass traits, physicochemical characteristics and fatty acid profile of meat, two experimental groups (six animals in each group) of male Merino lambs with different body weights (BW) at birth (low BW (LW; 3.88 ± 0.281 kg) and high BW (HW; 5.80 ± 0.647 kg)) were used. The lambs were penned with their corresponding ewe during the natural suckling period, being weaned at 15 kg. Then, the lambs were penned individually and offered a complete pelleted diet during the fattening period. All the animals were slaughtered when they reached 27 kg of BW. After weaning, both daily dry matter intake (578 vs. 615 g/day; p = 0.021) and average daily gain (141 vs. 190 g/day; p = 0.004) were significantly lower in LW lambs, and a higher feed:gain ratio was recorded for this group (3.98 vs. 3.45; p = 0.008). Carcass traits did not show differences (p > 0.05) between both groups of lambs, except for higher chilling losses for the LW group (3.29 vs. 2.69%; p = 0.012). Additionally, higher amounts of kidney knob and channel fat were observed for LW lambs (85.4 vs. 152 g; p = 0.028). Apart from a higher hardness of meat in LW lambs (152 vs. 189 Newtons, p = 0.040), no other differences (p > 0.05) were observed in the physicochemical traits of this product; however, the meat of LW lambs tended (p = 0.057) to contain more total fatty acid content with a higher (p = 0.041) proportion of saturated fatty acids than the meat of HW lambs. In conclusion, under the conditions of the present study, a low body weight at birth increased the deposition of fat in carcass and non-carcass components during the fattening period of lambs, thus reducing animal performance and worsening the nutritional indexes of the meat. Accordingly, it seems reasonable to try to identify these animals during early life, to be sold as suckling lambs in the meat market instead of being fattened.

Label-free quantitative proteomic analysis of M. longissimus dorsi from cattle during dietary restriction and subsequent compensatory growth

Compensatory growth (CG) is a naturally occurring physiological process whereby an animal has the ability to undergo enhanced growth following a period of restricted feeding. This studies objective was to identify key proteins involved in the expression of CG. Forty Holstein Friesian bulls were equally assigned to one of four groups. R1 and R2 groups were subjected to restricted feed allowance for 125 days (Period 1). A1 and A2 animals had ad libitum access to feed in Period 1. Following Period 1, all animals from R1 and A1 were slaughtered. Remaining animals (R2 and A2) were slaughtered following ad libitum access to feed for successive 55 days (Period 2). M. longissimus dorsi samples were collected at slaughter from all animals. Proteins were isolated from samples and subjected to label-free mass spectrometry proteomic quantification. Proteins which were differentially abundant during CG (n = 39) were involved in cellular binding processes, oxidative phosphorylation and mitochondrial function. There was also evidence for up regulation of three pathways involved in nucleotide biosynthesis. Genetic variants in or regulating genes pertaining to proteins identified in this study may hold potential for use as DNA based biomarkers for genomic selection of animals with a greater ability to undergo CG.

Food Restriction is Required to Preserve the Antisteatotic Effects of Central Leptin in the Liver of Middle-Aged Rats

OBJECTIVE

Aging is a significant risk factor for the development of obesity and hepatic steatosis associated with insulin and leptin resistance. Food restriction (FR) is commonly used for reducing body weight (BW), adiposity, and liver steatosis. Thus, this study aimed to determine whether FR in middle-aged rats can recover the central leptin antisteatotic effects observed in the liver in young animals.

METHODS

Two groups of 4-month-old Wistar rats were fed ad libitum (AL) or were on FR for 3 months. At 7 months of age, both groups were centrally treated with rat leptin (0.2 μg/d, 7 days) or saline.

RESULTS

Central leptin reduced food intake and BW, but not the hepatic triglyceride content, in 7-month-old rats fed AL. However, in 7-month-old FR rats, leptin did not affect BW but markedly reduced serum leptin, serum and hepatic triglyceride levels, and the expression of hepatic lipogenic genes. In addition, central leptin decreased serum and hepatic endogenous norepinephrine levels of FR rats, exerting a homeostatic effect beyond its antisteatotic actions.

CONCLUSIONS

These findings suggest that in middle-aged rats, moderate FR is required for both preserving the antisteatotic actions of central leptin and avoiding excessive weight loss.

Hepatocyte nuclear factors as possible C-reactive protein transcriptional inducer in the liver and white adipose tissue of rats with experimental chronic renal failure

Inflammation related to chronic kidney disease (CKD) is an important clinical problem. We recently determined that hepatocyte nuclear factor 1α (HNF1α) was upregulated in the livers of chronic renal failure (CRF) rats—experimental model of CKD. Considering that the promoter region of gene encoding C-reactive protein (CRP) contains binding sites for HNF1α and that the loss-of-function mutation in the Hnfs1α leads to significant reduction in circulating CRP levels, we hypothesized that HNF1α can activate the Crp in CRF rats. Here, we found coordinated upregulation of genes encoding CRP, interleukin-6 (IL-6), HNF1α, and HNF4α in the livers and white adipose tissue (WAT) of CRF rats, as compared to the pair-fed and control animals. This was accompanied by elevated serum levels of CRP and IL-6. CRP and HNFs’ mRNA levels correlated positively with CRP and HNFs’ protein levels in the liver and WAT. Similar upregulation of the Crp, Il-6, and Hnfs in the liver and WAT and increased serum CRP and IL-6 concentrations were found in lipopolysaccharide (LPS)-induced systemic inflammation in rats. Moreover, silencing HNF1α in HepG2 cells by small interfering RNA led to decrease in CRP mRNA levels. Our results suggests that (a) HNFs act in concert with IL-6 in the upregulation of CRP production by the liver and WAT, leading to an increase in circulating CRP concentration in CRF rats and (b) CRF-related inflammation plays an important role in the upregulation of genes that encode HNFs and CRP in the liver and WAT of CRF rats.

Programming Merino lambs by early feed restriction reduces growth rates and increases fat accretion during the fattening period with no effect on meat quality traits

The objective of the study was to determine the effect of early feed restriction on carcass and meat quality traits in Merino lambs. Twenty-four male Merino lambs (4.81±0.256kg) were assigned to two groups (12 animals in each group). The first group (ad libitum, ADL) was kept permanently with the dams. The second group (restricted, RES) was milk-restricted. After weaning (15kg), daily feed intake of all lambs was identical, but a lower gain: feed ratio was recorded in the RES group (0.320 vs. 0.261; P<0.001). After animals were slaughtered (27kg), lower ultimate pH and reduced yellow colouration of subcutaneous fat was recorded in meat from the RES lambs when compared to ADL group, whereas a trend towards a significant increment of intramuscular fat content and no effect on meat quality traits was observed in the RES lambs. Early feed restriction may be useful to increase intramuscular fat accretion in Merino lambs during the fattening period.

Long-term fructose consumption prolongs hepatic stearoyl-CoA desaturase 1 activity independent of upstream regulation in rats

Dietary fructose is considered a risk factor for metabolic disorders, such as fatty liver disease. However, the mechanism underlying the effects of fructose is not well characterized. We investigated the hepatic expression of key regulatory genes related to lipid metabolism following fructose feeding under well-defined conditions. Rats were fed standard chow supplemented with 10% w/v fructose solution for 5 weeks, and killed after chow-fasting and fructose withdrawal (fasting) or chow-fasting and continued fructose (fructose alone) for 14 h. Hepatic deposition of triglycerides was found in rats from both groups. As expected, fructose alone increased mRNA levels of lipogenesis-related genes and correspondingly decreased mRNA levels of lipid oxidative genes in the liver. Interesting, hepatic levels of stearoyl-CoA desaturase (SCD)1 mRNA remained elevated under fructose withdrawn conditions, although expression levels of other genes, including two key transcription factors (carbohydrate response element binding protein (ChREBP) and sterol regulatory element-binding protein (SREBP)-1c) fell to normal levels, indicating that long-term fructose intake increased SCD1 activity, independent of upstream regulatory genes, such as ChREBP and SREBP-1c. In conclusion, SCD1 overexpression in fatty liver disease is not affected by fasting after long-term fructose consumption in rats. Regulation of SCD1 plays an important role in fructose-induced hepatic steatosis.

Upregulation of Pnpla2 and Abhd5 and downregulation of G0s2 gene expression in mesenteric white adipose tissue as a potential reason for elevated concentration of circulating NEFA after removal of retroperitoneal, epididymal, and inguinal adipose tissue

Elevated concentrations of circulating non-esterified fatty acids (NEFA) were reported in (a) humans with lipodystrophy, (b) humans following bariatric surgery, and (c) transgenic mice with reduced amounts of adipose tissue. Paradoxically, these findings suggest that the reduction of adipose tissue mass is associated with elevated circulating NEFA concentrations. To explain a molecular background of this phenomenon, we analyzed the effects of surgical removal of inguinal, epididymal, and retroperitoneal white adipose tissue (WAT) on (a) circulating NEFA concentrations, (b) expression of Pnpla2, a gene that encodes adipose triglyceride lipase (ATGL), genes encoding abhydrolase domain containing 5 (ABHD5) and G0/G1 switch 2 (G0S2), i.e., a coactivator and inhibitor of ATGL, respectively, and (c) expression of Lipe gene coding hormone-sensitive lipase (HSL) in mesenteric WAT. Reduction of adipose tissue mass resulted in an increase in circulating NEFA concentration, which was associated with (a) an increase in the expressions of Pnpla2 and Abhd5, (b) decrease in G0s2 expression, and (c) upregulation of Lipe expression, all measured on both mRNA and protein levels in mesenteric WAT of male rats. The rate of lipolysis in mesenteric WAT explants and isolated adipocytes from lipectomized rats was significantly higher than that from the controls. In conclusion, upregulation of Pnpla2 expression and activation of ATGL (due to an increase in ABHD5 and decrease in G0S2 levels), as well as a coordinated interplay of these genes with Lipe in mesenteric WAT, contribute, at least in part, to an increase in the concentration of circulating NEFA in rats with reduced fat mass.

A return to ad libitum feeding following caloric restriction promotes hepatic steatosis in hyperphagic OLETF rats

Hyperphagic Otsuka Long-Evans Tokushima fatty (OLETF) rats develop obesity, insulin resistance, and nonalcoholic fatty liver disease (NAFLD), but lifestyle modifications, such as caloric restriction (CR), can prevent these conditions. We sought to determine if prior CR had protective effects on metabolic health and NAFLD development following a 4-wk return to ad libitum (AL) feeding. Four-week-old male OLETF rats (n = 8-10/group) were fed AL for 16 wk (O-AL), CR for 16 wk (O-CR; ∼70% kcal of O-AL), or CR for 12 wk followed by 4 wk of AL feeding (O-AL4wk). CR-induced benefit in prevention of NAFLD, including reduced hepatic steatosis, inflammation, and markers of Kupffer cell activation/number, was largely lost in AL4wk rats. These findings occurred in conjunction with a partial loss of CR-induced beneficial effects on obesity and serum triglycerides in O-AL4wk rats, but in the absence of changes in serum glucose or insulin. CR-induced increases in hepatic mitochondrial respiration remained significantly elevated (P < 0.01) in O-AL4wk compared with O-AL rats, while mitochondrial [1-(14)C]palmitate oxidation, citrate synthase activity, and β-hydroxyacyl-CoA dehydrogenase activity did not differ among OLETF groups. NAFLD development in O-AL4wk rats was accompanied by increases in the protein content of the de novo lipogenesis markers fatty acid synthase and stearoyl-CoA desaturase-1 and decreases in phosphorylated acetyl-CoA carboxylase (pACC)/ACC compared with O-CR rats (P < 0.05 for each). The beneficial effects of chronic CR on NAFLD development were largely lost with 4 wk of AL feeding in the hyperphagic OLETF rat, highlighting the importance of maintaining energy balance in the prevention of NAFLD.

Effect of Dietary Restriction and Subsequent Re-Alimentation on the Transcriptional Profile of Bovine Skeletal Muscle

Compensatory growth (CG), an accelerated growth phenomenon which occurs following a period of dietary restriction is exploited worldwide in animal production systems as a method to lower feed costs. However the molecular mechanisms regulated CG expression remain to be elucidated fully. This study aimed to uncover the underlying biology regulating CG in cattle, through an examination of skeletal muscle transcriptional profiles utilising next generation mRNA sequencing technology. Twenty Holstein Friesian bulls were fed either a restricted diet for 125 days, with a target growth rate of 0.6 kg/day (Period 1), following which they were allowed feed ad libitum for a further 55 days (Period 2) or fed ad libitum for the entirety of the trial. M. longissimus dorsi biopsies were harvested from all bulls on days 120 and 15 of periods 1 and 2 respectively and RNAseq analysis was performed. During re-alimentation in Period 2, previously restricted animals displayed CG, growing at 1.8 times the rate of the ad libitum control animals. Compensating animals were also more feed efficient during re-alimentation and compensated for 48% of their previous dietary restriction. 1,430 and 940 genes were identified as significantly differentially expressed (Benjamini Hochberg adjusted P < 0.1) in periods 1 and 2 respectively. Additionally, 2,237 genes were differentially expressed in animals undergoing CG relative to dietary restriction. Dietary restriction in Period 1 was associated with altered expression of genes involved in lipid metabolism and energy production. CG expression in Period 2 occurred in association with greater expression of genes involved in cellular function and organisation. This study highlights some of the molecular mechanisms regulating CG in cattle. Differentially expressed genes identified are potential candidate genes for the identification of biomarkers for CG and feed efficiency, which may be incorporated into future breeding programmes.

Age-Related Changes in Sirtuin 7 Expression in Calorie-Restricted and Refed Rats

Background: Sirtuins (SIRT1-7) have been implicated to mediate the beneficial effects of calorie restriction for healthy aging. While the physiological functions of SIRT7 are still poorly understood, SIRT7 has recently been shown to affect ribosome biogenesis, mitochondrial gene expression, and hepatic lipid metabolism. Objective: To analyze the effects of age and short-term calorie restriction (SCR) and subsequent refeeding on SIRT7 expression in key metabolic tissues. Methods: Four- and 24-month-old male Wistar rats were subjected to 40% SCR for 30 days, followed by ad libitum feeding for 2 or 4 days. Liver, white adipose tissue (WAT), heart and skeletal muscle samples were analyzed by real-time PCR and Western blotting for SIRT7 mRNA and protein expression, respectively. Results: Aging had diverse effects on SIRT7 levels in lipogenic tissues: both the mRNA and protein levels increased in the retroperitoneal depot (rWAT), did not change in the epididymal depot (eWAT), and decreased in the subcutaneous depot (sWAT) and the liver of old as compared to young animals. In the heart, extensor digitorum longus muscle (EDL) and soleus muscle (SOL), Sirt7 gene but not protein expression was lower in old than in young control rats. SCR did not affect SIRT7 expression in WAT and the liver in both age groups. In the heart of young animals, SCR did not affect SIRT7 mRNA or protein level. In EDL, SIRT7 protein but not mRNA levels decreased after SCR and remained reduced upon refeeding. In SOL, both SIRT7 mRNA and protein expression were inhibited by refeeding. In old rats, cardiac Sirt7 expression increased after SCR and refeeding. In old rats' EDL and SOL muscles, SIRT7 protein expression was inhibited by refeeding. Conclusion: Age-related changes of SIRT7 gene expression in key organs of energy homeostasis are tissue dependent.

Up-regulation of liver Pcsk9 gene expression as a possible cause of hypercholesterolemia in experimental chronic renal failure

Dyslipidemia commonly present in patients with chronic kidney disease (CKD) has been recently linked to increased proprotein convertase subtilisin/kexin type 9 (PCSK9) serum concentration. We tested a hypothesis that increased liver PCSK9 biosynthesis could be partially responsible for the elevated circulating PCSK9 level, and subsequently contribute to hypercholesterolemia observed in subjects with CKD. Rat model of chronic renal failure (CRF) was used in the study. Animals underwent a 5/6 nephrectomy or a sham operation. Liver expression of Pcsk9, sterol regulatory element-binding transcription factor 2 (Srebf-2), and β-actin were quantified by real-time RT-PCR. Liver protein levels of PCSK9, LDL-receptor (LDL-R), and SREBF-2 were analyzed using Western blotting. Serum PCSK9 concentration was estimated by immunoassay. Rats with an experimental CRF as compared to pair-fed and control ones were characterized by: (a) an up-regulation of liver Pcsk9 and Srebf-2 genes expression with parallel increase of serum PCSK9 concentration; (b) a decrease in liver LDL-R protein level, and (c) an increase of serum total and LDL-cholesterol concentrations. We also found significant correlations between serum creatinine and liver PCSK9 mRNA levels (r = 0.88, p < 0.001) and between serum creatinine and circulating PCSK9 levels (r = 0.73, p < 0.001). The results suggest that a rat model of CRF is associated with an increased liver Pcsk9 gene expression. The coordinated up-regulation of Pcsk9 and Srebf-2 genes expression suggests that SREBF-2 may play a key role in regulation of Pcsk9 gene expression, circulating PCSK9 level, and hypercholesterolemia in experimental CRF.

Fasting enriches liver triacylglycerol with n-3 polyunsaturated fatty acids: implications for understanding the adipose-liver axis in serum docosahexaenoic acid regulation

We investigated the effect of short-term fasting on coordinate changes in the fatty acid composition of adipose triacylglycerol (TAG), serum non-esterified fatty acids (NEFA), liver TAG, and serum TAG and phospholipids in mice fed ad libitum or fasted for 16 h overnight. In contrast to previous reports under conditions of maximal lipolysis, adipose tissue TAG was not preferentially depleted of n-3 PUFA or any specific fatty acids, nor were there any striking changes in the serum NEFA composition. Short-term fasting did, however, increase the hepatic proportion of n-3 PUFA, and almost all individual species of n-3 PUFA showed relative and absolute increases. The relative proportion of n-6 PUFA in liver TAG also increased but to a lesser extent, resulting in a significant decrease in the n-6:n-3 PUFA ratio (from 14.3 ± 2.54 to 9.6 ± 1.20), while the proportion of MUFA decreased significantly and SFA proportion did not change. Examination of genes involved in PUFA synthesis suggested that hepatic changes in the elongation and desaturation of precursor lipids could not explain this effect. Rather, an increase in the expression of fatty acid transporters specific for 22:6n-3 and other long-chain n-3 and n-6 PUFA likely mediated the observed hepatic enrichment. Analysis of serum phospholipids indicated a specific increase in the concentration of 22:6n-3 and 16:0, suggesting increased specific synthesis of DHA-enriched phospholipid by the liver for recirculation. Given the importance of blood phospholipid in distributing DHA to neural tissue, these findings have implications for understanding the adipose-liver-brain axis in n-3 PUFA metabolism.

Blood Cell Palmitoleate-Palmitate Ratio Is an Independent Prognostic Factor for Amyotrophic Lateral Sclerosis

Growing evidence supports a link between fatty acid metabolism and amyotrophic lateral sclerosis (ALS). Here we determined the fatty acid composition of blood lipids to identify markers of disease progression and survival. We enrolled 117 patients from two clinical centers and 48 of these were age and gender matched with healthy volunteers. We extracted total lipids from serum and blood cells, and separated fatty acid methyl esters by gas chromatography. We measured circulating biochemical parameters indicative of the metabolic status. Association between fatty acid composition and clinical readouts was studied, including ALS functional rating scale-revised (ALSFRS-R), survival, disease duration, site of onset and body mass index. Palmitoleate (16:1) and oleate (18:1) levels, and stearoyl-CoA desaturase indices (16:1/16:0 and 18:1/18:0) significantly increased in blood cells from ALS patients compared to healthy controls. Palmitoleate levels and 16:1/16:0 ratio in blood cells, but not body mass index or leptin concentrations, negatively correlated with ALSFRS-R decline over a six-month period (p<0.05). Multivariate Cox analysis, with age, body mass index, site of onset and ALSFRS-R as covariables, showed that blood cell 16:1/16:0 ratio was an independent prognostic factor for survival (hazard ratio=0.1 per unit of ratio, 95% confidence interval=0.01-0.57, p=0.009). In patients with high 16:1/16:0 ratio, survival at blood collection was extended by 10 months, as compared to patients with low ratio. The 16:1/16:0 index is an easy-to-handle parameter that predicts survival of ALS patients independently of body mass index. It therefore deserves further validation in larger cohorts for being used to assess disease outcome and effects of disease-modifying drugs.

Epigenetic regulation of the ELOVL6 gene is associated with a major QTL effect on fatty acid composition in pigs

Background

In previous studies on an Iberian x Landrace cross, we have provided evidence that supported the porcine ELOVL6 gene as the major causative gene of the QTL on pig chromosome 8 for palmitic and palmitoleic acid contents in muscle and backfat. The single nucleotide polymorphism (SNP) ELOVL6:c.-533C > T located in the promoter region of ELOVL6 was found to be highly associated with ELOVL6 expression and, accordingly, with the percentages of palmitic and palmitoleic acids in longissimus dorsi and adipose tissue. The main goal of the current work was to further study the role of ELOVL6 on these traits by analyzing the regulation of the expression of ELOVL6 and the implication of ELOVL6 polymorphisms on meat quality traits in pigs.

Results

High-throughput sequencing of BAC clones that contain the porcine ELOVL6 gene coupled to RNAseq data re-analysis showed that two isoforms of this gene are expressed in liver and adipose tissue and that they differ in number of exons and 3’UTR length. Although several SNPs in the 3’UTR of ELOVL6 were associated with palmitic and palmitoleic acid contents, this association was lower than that previously observed with SNP ELOVL6:c.-533C > T. This SNP is in full linkage disequilibrium with SNP ELOVL6:c.-394G > A that was identified in the binding site for estrogen receptor alpha (ERα). Interestingly, the ELOVL6:c.-394G allele is associated with an increase in methylation levels of the ELOVL6 promoter and with a decrease of ELOVL6 expression. Therefore, ERα is clearly a good candidate to explain the regulation of ELOVL6 expression through dynamic epigenetic changes in the binding site of known regulators of ELOVL6 gene, such as SREBF1 and SP1.

Conclusions

Our results strongly suggest the ELOVL6:c.-394G > A polymorphism as the causal mutation for the QTL on pig chromosome 8 that affects fatty acid composition in pigs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12711-015-0111-y) contains supplementary material, which is available to authorized users.

Progesterone-induced down-regulation of hormone sensitive lipase (Lipe) and up-regulation of G0/G1 switch 2 (G0s2) genes expression in inguinal adipose tissue of female rats is reflected by diminished rate of lipolysis

Decreased lipolytic activity in adipose tissue may be one of the reasons behind excess accumulation of body fat during pregnancy. The aim of this study was to analyze the effect of progesterone on the expression of: (a) Lipe (encoding hormone-sensitive lipase, HSL), (b) Pnpla2 (encoding adipose triglyceride lipase, ATGL), (c) abhydrolase domain containing 5 (Abhd5), and (d) G0/G1 switch 2 (G0s2) genes in white adipose tissue (WAT), as potential targets for progesterone action during the course of pregnancy. Administration of progesterone to female rats, which was reflected by approximately 2.5-fold increase in circulating progesterone concentration, is associated with a decrease in Lipe gene expression in the inguinal WAT. The expression of Pnpla2 gene in all main fat depots of females and males remained unchanged after progesterone administration. Administration of progesterone resulted in an increase in the expression of Abhd5 gene (whose product increases ATGL activity) and G0s2 gene (whose product decreases ATGL activity) in the inguinal WAT of female rats. Mifepristone, a selective antagonist of progesterone receptor, abolished the effect of progesterone on Lipe, Abhd5 and G0s2 genes expression in the inguinal WAT. The decrease in Lipe and the increase in Abhd5 and G0s2 genes expression was associated with lower rate of stimulated lipolysis. Administration of progesterone exerted no effect on Lipe, Abhd5 and G0s2 genes expression and stimulated lipolysis in the retroperitoneal WAT of females, as well as in the inguinal, epididymal and retroperitoneal WAT of males. In conclusion, our findings suggest that progesterone decreases the rate of lipolysis in the inguinal WAT of female rats, inhibiting the activity of both ATGL (by stimulating synthesis of G0S2 - specific inhibitor of the enzyme) and HSL (due to inhibition of Lipe gene expression).

White Adipose Tissue Depot-Specific Activity of Lipogenic Enzymes in Response to Fasting and Refeeding in Young and Old Rats

BACKGROUND

Although the heterogeneity of white adipose tissue (WAT) in different anatomical sites is a well-known phenomenon, there are scarce data on aging-associated metabolic alterations in various WAT depots.

OBJECTIVE

We used the model of fasting and refeeding to analyze the effect of aging on the activity of key lipogenic enzymes in retroperitoneal (rWAT), epididymal (eWAT), and subcutaneous (sWAT) adipose tissue depots.

METHODS

5- and 24-month-old male Wistar rats were fasted for 48 h or were fasted for 2 days and subsequently refed for 2 or 4 days. Control animals had ad libitum access to chow. Samples obtained from three WAT deposits were analyzed for the enzymatic activities of ATP citrate lyase (ACL), fatty acid synthase (FAS), and glucose-6-phosphate dehydrogenase (G6PD). Concentrations of lipids and proteins were measured in the blood serum.

RESULTS

Fasting for 2 days decreased the concentration of free fatty acids only in the young rats. The basal activities of ACL and FAS were lower in eWAT than in rWAT and sWAT of the young rats. In the young rats, fasting did not change ACL and FAS activities in any of the studied depots. Refeeding increased these activities more quickly in rWAT than in eWAT, while in sWAT no induction was observed. ACL and FAS activities were manifold lower in all WAT depots of the old than in those of the young rats. In the old animals fasting had no effect on ACL activity in any depot and decreased FAS activity only in sWAT. After 4 days of refeeding, FAS activity increased in rWAT and sWAT, but no change in ACL activity occurred. G6PD activity in the young rats was lower by 40% in eWAT than in rWAT. The induction of the enzyme by refeeding occurred faster in rWAT than in eWAT, while in sWAT no change in G6PD activity was observed. G6PD activity did not change with aging. Fasting of the old rats decreased G6PD activity in rWAT and sWAT. Refeeding failed to induce the enzyme in these depots, whereas in eWAT G6PD activity increased by 76% after 4 days of refeeding.

CONCLUSION

Fasting and refeeding revealed WAT depot-specific, age-related changes of the activities of lipogenic enzymes.

Effect of seasonal and experimental temperature on de novo synthesis of fatty acids in C. crangon

The intensity of in vivo lipogensis was measured and in this purpose, the radioactivity of incorporation of tritium into fatty acids (FAs) in tissues of C. crangon was determined. De novo synthesis of FAs was five times higher in hepatopancreas than in muscle in summer period but not much higher in autumn. The higher FAs synthesis was recorded at 25 °C, both for hepatopancreas and muscle, and the summer was higher than the autumn in the hepatopancreas and in the muscles of the opposite situation was observed. The higher amounts of SFAs in hepatopancreas from autumn, when in experimental conditions the ambient temperature C. crangon changed from 6 °C to the experimental higher temperature. When content of PUFAn-3 declined dramatically (Autumn 1 h, 25 °C). In contrast, at a lower temperature, the amount of polyunsaturated FAs is much higher than at 25 °C (Autumn 1 h 6 °C).

Down-regulation of Zac1 gene expression in rat white adipose tissue by androgens

ZAC1 is a zinc-finger protein transcription factor, a transcriptional cofactor for nuclear receptors, and a co-activator of nuclear receptors, which interacts with multiple signaling pathways affecting apoptosis, cell cycle arrest, and metabolism. Some data suggest that ZAC1 regulates the expression of genes associated with function of adipose tissue. Since there is no information about the levels of Zac1 gene expression in white adipose tissue (WAT), and the expression of several genes associated with metabolic function of WAT is significantly lower in male than female animals, we have examined: (a) the relative ZAC1 mRNA levels in some organs/tissues, including three main depots of WAT, in 3-month-old male rats; (b) the relative ZAC1 mRNA levels in WAT of male and female rats; (c) the effect of orchidectomy and orchidectomy with concomitant testosterone treatment on ZAC1 mRNA and protein levels; (d) the effect of ovariectomy and ovariectomy with concomitant 17β-estradiol treatment on ZAC1 mRNA levels; (e) the effect of dihydrotestosterone on ZAC1 mRNA levels in isolated adipocytes. Our results indicate that: (a) ZAC1 mRNA levels are relatively high in WAT in comparison with other organs/tissues; (b) ZAC1 mRNA levels in subcutaneous WAT are approximately 2-fold lower than in epididymal and retroperitoneal adipose tissue; (c) ZAC1 mRNA levels in WAT of adult female rats are approximately 2-fold higher than in male rats; (d) testosterone is inversely related to ZAC1 mRNA and protein levels in WAT of male rats; and (e) dihydrotestosterone decreases the ZAC1 mRNA levels in adipocytes in dose dependent manner. In conclusion, Zac1 gene is highly expressed in white adipose tissue of adult rats. Androgens could play an important role in down-regulation of the ZAC1 mRNA and protein levels in rats.

Identification of cyclopropaneoctanoic acid 2-hexyl in human adipose tissue and serum

Fatty acids containing a cyclopropane ring in their structure (cyclopropane FA) have been found in a wide variety of bacteria, a number of protozoa, and Myriapoda. Little is known about cyclopropane FA in mammal, especially in human tissues. The present study deals with the identification of cyclopropane FA in adipose tissue and serum of humans and rats. Fatty acids extracted from the adipose tissue and serum obtained from obese women during bariatric surgery were methylated and analyzed on GC–MS. We have identified: cyclopropaneoctanoic acid 2-hexyl, cyclopropaneoctanoic acid 2-octyl, cyclopropanenonanoic acid, and 2-[[2-[(2-ethylcyclopropyl)methyl]cyclopropyl]methyl] acid in human adipose tissue. We confirmed the presence of cyclopropaneoctanoic acid 2-hexyl by derivatization of FA extracted from human adipose tissue to picolinyl esters. Cyclopropaneoctanoic acid 2-hexyl was the main cyclopropane FA (approximately 0.4 % of total fatty acids in human adipose tissue, and about 0.2 % of total fatty acids in the serum). In adipose tissue cyclopropaneoctanoic acid 2-hexyl was found mainly in triacylglycerols, whereas in serum in phospholipids and triacylglycerols. The cyclopropaneoctanoic acid 2-hexyl has also been found in serum, and adipose tissue of rats in amounts comparable to humans. The content of cyclopropaneoctanoic acid 2-hexyl decreased in adipose tissue of rats maintained on a restricted diet for 1 month. In conclusion, we demonstrated that cyclopropaneoctanoic acid 2-hexyl is present in human adipose tissue and serum. Adipose tissue cyclopropaneoctanoic acid 2-hexyl is stored mainly in triacylglycerols and the storage of this cyclopropane FA is affected by food restriction.

Up-regulation of lipogenic enzyme genes expression in inguinal white adipose tissue of female rats by progesterone

Contradictory results have been published regarding the influence of progesterone on lipids metabolism in adipose tissue. The aim of the present work was to elucidate whether progesterone administration in the setting of an experimental model influences lipogenic enzyme genes expression, body and adipose tissue mass. The results presented here indicate that the elevated blood progesterone concentration was associated with significant increase in lipogenic enzyme genes expression in inguinal adipose tissue of females. The rise in the expression of lipogenic enzyme genes was associated with an increase in sterol regulatory element binding transcription factor 1 (Srebf1) and S14 genes expression. Mifepristone, a specific antagonist of progesterone receptor, abolished progesterone's effect on body mass, inguinal fat mass, and lipogenic enzyme genes expression in inguinal adipose tissue. No significant changes were found in the expression of lipogenic enzyme genes, Srebf1 and S14 genes in perirenal white adipose tissue of females. The elevated blood progesterone concentration was associated with the increase in body and inguinal white adipose tissue mass of females. In males, elevated blood progesterone concentration had no effect on the lipogenic enzyme genes expression and on body and fat mass. In conclusion, we demonstrate that a chronic increase in serum progesterone concentration in females was associated with up-regulation of lipogenic enzyme genes expression in inguinal adipose tissue. Up-regulation of Srebf1 and S14 genes expression following progesterone administration suggests that products of these genes might be involved in the regulation of lipogenic enzyme genes expression by progesterone. The stimulatory effect of progesterone on lipogenic enzyme genes expression in inguinal adipose tissue seems to be specific as it was reversed by specific antagonist of progesterone receptor.

Polymorphism in the ELOVL6 gene is associated with a major QTL effect on fatty acid composition in pigs

Background

The ELOVL fatty acid elongase 6 (ELOVL6), the only elongase related to de novo lipogenesis, catalyzes the rate-limiting step in the elongation cycle by controlling the fatty acid balance in mammals. It is located on pig chromosome 8 (SSC8) in a region where a QTL affecting palmitic, and palmitoleic acid composition was previously detected, using an Iberian x Landrace intercross. The main goal of this work was to fine-map the QTL and to evaluate the ELOVL6 gene as a positional candidate gene affecting the percentages of palmitic and palmitoleic fatty acids in pigs.

Methodology and Principal Findings

The combination of a haplotype-based approach and single-marker analysis allowed us to identify the main, associated interval for the QTL, in which the ELOVL6 gene was identified and selected as a positional candidate gene. A polymorphism in the promoter region of ELOVL6, ELOVL6:c.-533C>T, was highly associated with the percentage of palmitic and palmitoleic acids in muscle and backfat. Significant differences in ELOVL6 gene expression were observed in backfat when animals were classified by the ELOVL6:c.-533C>T genotype. Accordingly, animals carrying the allele associated with a decrease in ELOVL6 gene expression presented an increase in C16:0 and C16:1(n-7) fatty acid content and a decrease of elongation activity ratios in muscle and backfat. Furthermore, a SNP genome-wide association study with ELOVL6 relative expression levels in backfat showed the strongest effect on the SSC8 region in which the ELOVL6 gene is located. Finally, different potential genomic regions associated with ELOVL6 gene expression were also identified by GWAS in liver and muscle, suggesting a differential tissue regulation of the ELOVL6 gene.

Conclusions and Significance

Our results suggest ELOVL6 as a potential causal gene for the QTL analyzed and, subsequently, for controlling the overall balance of fatty acid composition in pigs.

Hepatic and plasma sex differences in saturated and monounsaturated fatty acids are associated with differences in expression of elongase 6, but not stearoyl-CoA desaturase in Sprague-Dawley rats

Monounsaturated fatty acids (MUFA) have been viewed as either beneficial or neutral with respect to health; however, recent evidence suggests that MUFA may be associated with obesity and cardiovascular disease. Sex differences in MUFA composition have been reported in both rats and humans, but the basis for this sexual dimorphism is unknown. In the current study, enzymes involved in MUFA biosynthesis are examined in rat and cell culture models. Male and female rats were maintained on an AIN-93G diet prior to killing at 14 weeks of age after an overnight fast. Concentrations of 16:0 (2,757 ± 616 vs. 3,515 ± 196 μg fatty acid/g liver in males), 18:1n-7 (293 ± 66 vs. 527 ± 49 μg/g) and 18:1n-9 (390 ± 80 vs. 546 ± 47 μg/g) were lower, and concentrations of 18:0 (5,943 ± 1,429 vs. 3,987 ± 325 μg/g) were higher in phospholipids in livers from female rats compared with males. Hepatic elongase 6 mRNA and protein were 5.9- and 2.0-fold higher, respectively, in females compared with males. Stearoyl-CoA desaturase expression did not differ. Specific hormonal effects were examined in HepG2 cells cultured with varying concentrations of 17β-estradiol, progesterone and testosterone (0, 10, 30 and 100 nM) for 72 h. Progesterone and 17β-estradiol treatments increased, while testosterone decreased, elongase 6 protein. Sex differences in MUFA composition were associated with increased expression of hepatic elongase 6 in females relative to male rats, which appears to be mediated by sex hormones based on observations of hormonal treatments of HepG2 cells.

The gender- and fat depot-specific regulation of leptin, resistin and adiponectin genes expression by progesterone in rat

Progesterone affects lipid metabolism in adipose tissue and influences fat distribution in human. The aim of the study was to analyze the effect of progesterone on rat body and fat mass and on expression of genes encoding adipokines involved in the regulation of energy homeostasis. The results presented here indicate that progesterone administration to females caused increase in body and inguinal white adipose tissue mass. The increase of inguinal white adipose tissue mass is associated with the hypertrophy of adipocyte. The same dose of progesterone caused increase of its circulating concentration in males, however it barely reached the value observed in non-treated control females and did not have any effect on body and fat mass. The elevated circulating progesterone concentration was associated with an approximately 6- and 2-fold increase of leptin and resistin mRNA level respectively, and 2-fold decrease of adiponectin mRNA level only in inguinal white adipose tissue of females. RU 486, specific antagonist of progesterone receptor, abolished the effect of progesterone on the adipokine mRNA level in inguinal adipose tissue. In males, the elevated circulating progesterone concentration showed no effects on leptin, resistin or adiponectin mRNA level in inguinal, retroperitoneal or epididymal adipose tissue. Moreover, the results presented in this paper demonstrate a relatively high level of progesterone receptor mRNA in inguinal white adipose tissue of females, which was down-regulated in response to progesterone administration. In retroperitoneal adipose tissue of control females progesterone receptor mRNA level was approximately 3-fold lower as compared to inguinal adipose tissue. In inguinal, epididymal and retroperitoneal white adipose tissue of males progesterone receptor mRNA was hardly detected. Our results suggest that depot- and sex-dependent responsiveness of adipose tissue to the pharmacological dose of progesterone is controlled by both circulating concentration of progesterone and the white adipose tissue progesterone receptor level.