Fatty Acid Mobilization Research Articles

Specific shifts in the endocannabinoid system in hibernating brown bears

In small hibernators, global downregulation of the endocannabinoid system (ECS), which is involved in modulating neuronal signaling, feeding behavior, energy metabolism, and circannual rhythms, has been reported to possibly drive physiological adaptation to the hibernating state. In hibernating brown bears (Ursus arctos), we hypothesized that beyond an overall suppression of the ECS, seasonal shift in endocannabinoids compounds could be linked to bear’s peculiar features that include hibernation without arousal episodes and capacity to react to external disturbance. We explored circulating lipids in serum and the ECS in plasma and metabolically active tissues in free-ranging subadult Scandinavian brown bears when both active and hibernating. In winter bear serum, in addition to a 2-fold increase in total fatty acid concentration, we found significant changes in relative proportions of circulating fatty acids, such as a 2-fold increase in docosahexaenoic acid C22:6 n-3 and a decrease in arachidonic acid C20:4 n-6. In adipose and muscle tissues of hibernating bears, we found significant lower concentrations of 2-arachidonoylglycerol (2-AG), a major ligand of cannabinoid receptors 1 (CB1) and 2 (CB2). Lower mRNA level for genes encoding CB1 and CB2 were also found in winter muscle and adipose tissue, respectively. The observed reduction in ECS tone may promote fatty acid mobilization from body fat stores, and favor carbohydrate metabolism in skeletal muscle of hibernating bears. Additionally, high circulating level of the endocannabinoid-like compound N-oleoylethanolamide (OEA) in winter could favor lipolysis and fatty acid oxidation in peripheral tissues. We also speculated on a role of OEA in the conservation of an anorexigenic signal and in the maintenance of torpor during hibernation, while sustaining the capacity of bears to sense stimuli from the environment.

Probing metabolic memory in the hepatic response to fasting.

Tissues may respond differently to a particular stimulus if they have been previously exposed to that same stimulus. Here, we tested the hypothesis that a strong metabolic stimulus such as fasting may influence the hepatic response to a subsequent fast and thus elicit a memory effect. Overnight fasting in mice significantly increased plasma free fatty acids, glycerol, β-hydroxybutyrate, and liver triglycerides, and decreased plasma glucose, plasma triglycerides, and liver glycogen levels. In addition, fasting dramatically changed the liver transcriptome, upregulating genes involved in gluconeogenesis and in uptake, oxidation, storage, and mobilization of fatty acids, and downregulating genes involved in fatty acid synthesis, fatty acid elongation/desaturation, and cholesterol synthesis. Fasting also markedly impacted the liver metabolome, causing a decrease in the levels of numerous amino acids, glycolytic-intermediates, TCA cycle intermediates, and nucleotides. However, these fasting-induced changes were unaffected by two previous overnight fasts. Also, no significant effect was observed of prior fasting on glucose tolerance. Finally, analysis of the effect of fasting on the transcriptome in hepatocyte humanized mouse livers indicated modest similarity in gene regulation in mouse and human liver cells. In general, genes involved in metabolic pathways were upregulated or downregulated to a lesser extent in human liver cells than in mouse liver cells. In conclusion, we found that previous exposure to fasting in mice did not influence the hepatic response to a subsequent fast, arguing against the concept of metabolic memory in the liver. Our data provide a useful resource for the study of liver metabolism during fasting.

Respiratory quotient: Effects of fatty acid composition

Respiratory quotient (RQ) is commonly used to infer which substrates are oxidized, with glucose yielding RQ = 1 and fat normally thought to yield an average of RQ = 0.71. Because fat depot compositions differ among species, we examined how the various common fatty acids affect RQ. RQs ranged from less than 0.7 (e.g., stearic acid) to greater than 0.76 (e.g., docosahexaenoic acid). Furthermore, we conducted a survey of the fatty acid composition of fuel lipids of several vertebrate taxa to determine how the RQ for lipid oxidation during fasting should vary among species. Our survey indicates that most fasting vertebrates from terrestrial ecosystems oxidizing fat should have RQs equaling approximately 0.71, as normally expected. However, some fasting animals in aquatic or marine systems-particularly fish-should have RQs as high as 0.73 when oxidizing only fat. Selective mobilization of fatty acids increased the lipid RQ, but probably by a negligible amount. We conclude that researchers should take habitat and taxon into account when choosing a value for lipid RQ, and preferably should use fatty acid composition for their study species to determine an appropriate RQ for lipids. In the absence of species-specific fatty acid composition data, we suggest assuming a lipid RQ of 0.725 for cold-water fish.

Cardiotrophin-1 contributes to metabolic adaptations through the regulation of lipid metabolism and to the fasting-induced fatty acid mobilization.

It is becoming clear that several human pathologies are caused by altered metabolic adaptations. During liver development, there are physiological changes, from the predominant utilization of glucose (fetal life) to the use of lipids (postnatal life). Fasting is another physiological stress that elicits well-known metabolic adjustments. We have reported the metabolic properties of cardiotrophin-1 (CT-1), a member of the interleukin-6 family of cytokines. Here, we aimed at analyzing the role of CT-1 in response to these metabolic changes. We used different in vivo models. Furthermore, a differential study was carried out with wild-type and CT-1 null mice in fed (ad libitum) and food-restricted conditions. We demonstrated that Ct-1 is a metabolic gene induced in the liver via PPARα in response to lipids in mice (neonates- and food-restricted adults). We found that Ct-1 mRNA expression in white adipose tissue directly involved PPARα and PPARγ. Finally, the physiological role of CT-1 in fasting is confirmed by the impaired food restriction-induced adipose tissue lipid mobilization in CT-1 null mice. Our findings support a previously unrecognized physiological role of CT-1 in metabolic adaptations, through the regulation of lipid metabolism and contributes to fasting-induced free fatty acid mobilization.

Alpha-lipoic acid improves the reproduction performance of breeder hens during the late egg-laying period.

Alpha-lipoic acid (ALA), a multifunctional antioxidant, can promote fatty acid mobilization, energy expenditure and scavenge free radicals. The effects of dietary ALA on the reproductive performance of breeder hens were investigated in the current study. In the 5-week experiment, 180 54-week-old Qiling breeder hens were randomly divided into three treatments with five replicates and supplemented with three levels of ALA (0, 300 and 600mg/kg) in the basic corn-soya bean meal diets. 600mg/kg ALA treatment group (HLA) significantly improved the eggshell thickness and strength (p<.05). ALA-treated groups improved egg-laying rate compared with the CON group, but with no statistically significant difference (p>.05). The levels of HDL-C, ALB and estradiol (E2) of the serum in the HLA group were elevated compared with the CON group (p<.05). In addition, ALA (600mg/kg) treatment exhibited a reduced level of serum AST and TG (p<.05). Dietary ALA increased the activity of hepatic lipase in liver (p<.05). Supplemental 600mg/kg ALA also improved the SOD activity and total antioxidant capacity level, along with a decreased MDA in ovarian tissue (p<.05). Furthermore, the mRNA expressions of ESR1, ESR2, VTG2 and ApoB in the liver and FSHR in follicles were upregulated in the HLA group (p<.05). In conclusion, dietary supplementation with 600mg/kg ALA during the late egg-laying period could improve lipid metabolism and reproductive performance of breeder hens.

Effect of augmented glycation in mobilization of plasma free fatty acids in type 2 diabetes mellitus

Background and aimsType 2 Diabetes Mellitus (T2DM) is known to be associated with an increase in total plasma free fatty acid (FFA) concentration. The present study was conducted to determine the changes in plasma fatty acids at different levels of glycation in type 2 diabetes mellitus. MethodsThe study involved 50 subjects having different levels of glycation (HbA1c 4.9–15.0%) and further categorized in 5 groups [group 1 (HbA1c <6%), group 2 (HbA1c 6–7%), group 3 (HbA1c 7.1–9%), group 4 (HbA1c (9.1–12%) and group 5 (HbA1c >12%)] with 10 subjects in each group. ResultsA total of 19 free fatty acids were detected by gas chromatography-mass spectrometry (GC-MS) analysis in the plasma samples. The levels of lauric acid (C12:0) and stearic acid (C18:0) were significantly raised at an advanced stage of glycation (HbA1c 9.1–15%). Long-chain fatty acids, pentadecanoic acid (C15:0) and palmitic acid (C16:0) levels were elevated in hyperglycemia as compared to normoglycaemic subjects (HbA1c <6%). Moreover, levels of mono and polyunsaturated fatty acids, oleic acid (C18:1) and linoleic acid (C18:2, w6) were significantly decreased in patients with increased levels of glycation (HbA1c 6–15%). Conclusion: GC-MS is a novel way to study the plasma fatty acid profiling and findings of this study suggest that monitoring alterations in plasma FFA profile may be of prognostic value.

Role of Elevated Intracellular S-Adenosylhomocysteine in the Pathogenesis of Alcohol-Related Liver Disease.

Background: The earliest manifestation of alcohol-related liver disease (ALD) is steatosis, characterized by the accumulation of lipid droplets (LDs) in hepatocytes. Findings from our laboratory have indicated that many pathological changes, including steatosis, correlate with the alcohol-induced hepatocellular increases in S-adenosylhomocysteine (SAH). Based on these considerations, we hypothesized that an experimental increase in intracellular SAH alone will result in similar steatotic changes to those seen after alcohol exposure. Methods: Freshly isolated rat hepatocytes grown on collagen-coated plates were exposed to serum-free medium containing 50 µmol/L oleic acid and varying concentrations of 3-deazaadenosine (DZA) to experimentally elevate intracellular SAH levels. Results: Overnight exposure to DZA treatment dose-dependently increased hepatocellular triglyceride accumulation, which was also evident by morphological visualization of larger-sized LDs. The rise in triglycerides and LDs accompanied increases in mRNA and protein levels of several LD-associated proteins known to regulate LD number and size. Furthermore, DZA treatment caused a decline in the levels of lipases that prevent fat accumulation as well as increased the expression of factors involved in lipogenesis and fatty acid mobilization. Collectively, our results indicate that the elevation of intracellular SAH is sufficient to promote fat accumulation in hepatocytes, which is similar to that seen after alcohol exposure.

Metabolic Effects of Late Dinner in Healthy Volunteers-A Randomized Crossover Clinical Trial.

Consuming calories later in the day is associated with obesity and metabolic syndrome. We hypothesized that eating a late dinner alters substrate metabolism during sleep in a manner that promotes obesity. The objective of this work is to examine the impact of late dinner on nocturnal metabolism in healthy volunteers. This is a randomized crossover trial of late dinner (LD, 22:00) vs routine dinner (RD, 18:00), with a fixed sleep period (23:00-07:00) in a laboratory setting. Participants comprised 20 healthy volunteers (10 male, 10 female), age 26.0 ± 0.6 years, body mass index 23.2 ± 0.7 kg/m2, accustomed to a bedtime between 22:00 and 01:00. An isocaloric macronutrient diet was administered on both visits. Dinner (35% daily kcal, 50% carbohydrate, 35% fat) with an oral lipid tracer ([2H31] palmitate, 15 mg/kg) was given at 18:00 with RD and 22:00 with LD. Measurements included nocturnal and next-morning hourly plasma glucose, insulin, triglycerides, free fatty acids (FFAs), cortisol, dietary fatty acid oxidation, and overnight polysomnography. LD caused a 4-hour shift in the postprandial period, overlapping with the sleep phase. Independent of this shift, the postprandial period following LD was characterized by higher glucose, a triglyceride peak delay, and lower FFA and dietary fatty acid oxidation. LD did not affect sleep architecture, but increased plasma cortisol. These metabolic changes were most pronounced in habitual earlier sleepers determined by actigraphy monitoring. LD induces nocturnal glucose intolerance, and reduces fatty acid oxidation and mobilization, particularly in earlier sleepers. These effects might promote obesity if they recur chronically.

1083-P: Bromocriptine-QR (BQR) Reduces Hypertriglyceridemia (HTG) in Hypertensive Type 2 Diabetes (T2D) Subjects

Chronically elevated sympathetic nervous system (SNS) activity increases hepatic triglyceride (TG) synthesis and secretion and adipose free fatty acid mobilization leading to further hepatic TG synthesis and HTG. HTG often occurs in the presence of hypertension and this can be a biomarker of chronically elevated SNS activity. BQR, a dopamine agonist, is the only sympatholytic antidiabetes agent approved for T2D. Preclinical studies have repeatedly demonstrated that circadian-timed bromocriptine therapy ameliorates HTG. This study evaluated if circadian-timed BQR (1.6-4.8 mg/day) reduces HTG in a population of hypertensive HTG T2D subjects. Hypertensive HTG T2D subjects from the Cycloset Safety Trial (HbA1c ≥ 7.0) treated at baseline with diet +/- any one or two antidiabetes agents of sulfonylurea, metformin, thiazolidinedione or insulin (N = 378) and randomized to BQR or placebo for 24 weeks were analyzed for between group difference in change from baseline fasting plasma TG level. After 24 weeks of therapy, BQR significantly reduced fasting TG levels by between 34 to 219 mg/dl (13 to 36%) and HbA1c from -0.4 to -1.2 as the baseline fasting TG level rose from ≥ 150 to ≥ 400 mg/dl (Figure). These TG effects were even more pronounced in such subjects with elevated resting heart rate. Circadian-timed BQR reduces hypertriglyceridemia in T2D and this effect increases with increasing fasting TG level. Disclosure B. Chamarthi: Employee; Self; VeroScience LLC. M. Ezrokhi: Employee; Self; VeroScience LLC. A.H. Cincotta: Employee; Self; VeroScience LLC.

Effect of Black Coffee on Fasting Metabolic Markers and an Abbreviated Fat Tolerance Test

Abstract Objectives Common clinical recommendations direct patients to report fasted when blood work (e.g., triglycerides [TG], glucose [Glu]) will take place, which typically excludes black coffee consumption. Despite its negligible calorie content, caffeinated coffee increases fatty acid mobilization. However, whether this effect meaningfully alters fasting metabolic testing or influences the results of a fat tolerance test is unclear. We investigated whether allowing black coffee intake within a fast prior to blood work affected fasting TG and Glu, as well as the postprandial lipemic and glycemic response following an abbreviated fat tolerance test. Methods In a randomized crossover design, participants were instructed to consume only water, or were allowed 8 fluid ounces of black coffee at the end of a 10-hr fast. Next, TG and Glu were assessed using the Cholestech LDX system (Alere Cholestech: Hayward, CA, USA) before and after a previously validated 4-hr fat tolerance test (9 kcal/kg; 73% fat, 26% CHO). Paired t-tests were performed to assess baseline and 4-hr values, absolute change, and % change for both TG and Glu. Results Preliminary analysis of healthy subjects (n = 3 of 10 subjects completed; 1 M/2F; age 20.3 ± 2.3; BMI 25.7 ± 0.6) revealed that consuming coffee prior to the blood draw did not affect fasting TG (Mean difference (MD) = 7.0 mg/dL; P = 0.68). Similarly, the lipemic response was not altered by coffee, evidenced by no alterations in 4-hr TG (MD = 7.6 mg/dL), Δ TG (MD = 14.7 mg/dL), and % change in TG (MD = 29.1%; all P’s ≥ 0.52). Fasting Glu was unchanged following coffee consumption (MD = 29.1 mg/dL; P = 0.90), and indicators of the glycemic response such as 4-hr Glu (MD = 0.0 mg/dL), Δ Glu (MD = 1.0 mg/dL), and % change (MD = 1.2%), were similar among water and coffee trials (all P's ≥ 0.73). Conclusions At this point in the study, coffee consumption does not seem to alter fasting TG or markers of fat tolerance. Additionally, fasting Glu and the glycemic response do not appear to be influenced by coffee consumption. When completed, this study will help answer the practical question of whether coffee need be avoided prior to basic metabolic testing or a fat tolerance test, which may provide increased consistency in metabolic assessment and potentially improve patients’ clinical experience. Funding Sources Lew Wentz Research Scholars Program at Oklahoma State University.

3-Iodothyronamine Affects Thermogenic Substrates' Mobilization in Brown Adipocytes.

We investigated the effect of 3-iodothyronamine (T1AM) on thermogenic substrates in brown adipocytes (BAs). BAs isolated from the stromal fraction of rat brown adipose tissue were exposed to an adipogenic medium containing insulin in the absence (M) or in the presence of 20 nM T1AM (M+T1AM) for 6 days. At the end of the treatment, the expression of p-PKA/PKA, p-AKT/AKT, p-AMPK/AMPK, p-CREB/CREB, p-P38/P38, type 1 and 3 beta adrenergic receptors (β1–β3AR), GLUT4, type 2 deiodinase (DIO2), and uncoupling protein 1 (UCP-1) were evaluated. The effects of cell conditioning with T1AM on fatty acid mobilization (basal and adrenergic-mediated), glucose uptake (basal and insulin-mediated), and ATP cell content were also analyzed in both cell populations. When compared to cells not exposed, M+T1AM cells showed increased p-PKA/PKA, p-AKT/AKT, p-CREB/CREB, p-P38/P38, and p-AMPK/AMPK, downregulation of DIO2 and β1AR, and upregulation of glycosylated β3AR, GLUT4, and adiponectin. At basal conditions, glycerol release was higher for M+T1AM cells than M cells, without any significant differences in basal glucose uptake. Notably, in M+T1AM cells, adrenergic agonists failed to activate PKA and lipolysis and to increase ATP level, but the glucose uptake in response to insulin exposure was more pronounced than in M cells. In conclusion, our results suggest that BAs conditioning with T1AM promote a catabolic condition promising to fight obesity and insulin resistance.

The pharmacogenomics of asparaginase‐mediated toxicities in acute lymphoblastic leukemia (ALL) patients

The bacterial enzyme L‐asparaginase (ASNase) is an essential component of effective combination chemotherapy for the treatment of acute lymphoblastic leukemia (ALL). However, the development of immune‐mediated toxicities to this agent can increase the risk of leukemia relapse in children, whereas the high risk of liver injury limits the use of ASNase in adults despite its benefit on treatment outcome. The overarching goal of our studies is to understand the underlying molecular mechanisms of common asparaginase‐mediated toxicities that lead to poor treatment outcome by integrating genome‐wide association studies (GWAS) and experimental validations using genetic and pharmacological models.In the first example, we focused on ASNase‐induced immunotoxicity. We identified by GWAS a higher risk of ASNase immunotoxicity among carriers of the nuclear factor of activated T‐cells, cytoplasmic, calcineurin‐dependent 2 (NFATC2) rs6021191 variant, which leads to elevated expression of this transcription factor involved in the regulation of immune responses. Consistent with our GWAS results, we found the NFATc2‐deficient mice were protected from ASNase‐induced immunotoxicity. Furthermore, we have demonstrated that the pharmacological inhibition of the NFAT pathway in wild‐type mice yields similar protection as NFATc2 deficiency. Current research aims to develop a selective inhibitor of calcineurin‐mediated NFATc2 activation that is expected to attenuate ASNase‐induced immunotoxicity in pediatric ALL patients.In another example, we focused on ASNase‐induced hepatotoxicity, including steatosis. Our group led the first GWAS of ASNase hepatotoxicity and identified an association between the patatin‐like phospholipase domain‐containing 3 (PNPLA3) I148M variant and alanine aminotransferase (ALT) levels after ASNase therapy. The PNPLA3 I148M variant is associated with the development of non‐alcoholic liver disease (NAFLD) and our results are the first to link the variant to drug‐induced liver injury. Consistent with our GWAS, mice treated with ASNase develop fatty livers after a single dose. Additional studies elucidating the mechanism of the toxicity have identified a novel mechanism of drug‐induced liver injury involving ASNase‐induced adipose tissue lipolysis, systemic free fatty acid mobilization, hepatic triglyceride accumulation, and fatty acid‐induced liver injury. Our lab has further demonstrated that pharmacological inhibition of adipose triglyceride lipase (Atgl), which is a key enzyme involved in adipose lipolysis, protects from ASNase‐mediated liver injury. We believe inhibition of ASNase‐induced steatosis will help expand ASNase therapy to adult ALL patients.In summary, our studies are clinically relevant and highly translational. Our ultimate goal is to improve ALL survival by mitigating ASNase‐induced toxicities and ensuring that patients can benefit from the therapeutic effect of ASNase on leukemias.Support or Funding InformationThis study was supported by the University of Pittsburgh School of Pharmacy and the NIH Grant RO1 CA216815.

Ghrelin regulates adipose tissue metabolism: Role in hepatic steatosis

Fatty liver is the earliest and most common response of the liver to consumption of excessive alcohol. Steatosis can predispose the fatty liver to develop progressive liver damage. Chief among the many mechanisms involved in development of hepatic steatosis is dysregulation of insulin-mediated adipose tissue metabolism. Particularly, it is the enhanced adipose lipolysis-derived free fatty acids and their delivery to the liver that ultimately results in hepatic steatosis. The adipose-liver axis is modulated by hormones, particularly insulin and adiponectin. In recent studies, we demonstrated that an alcohol-induced increase in serum ghrelin levels impairs insulin secretion from pancreatic β-cells. The consequent reduction in circulating insulin levels promotes adipose lipolysis and mobilization of fatty acids to the liver to ultimately contribute to hepatic steatosis. Because many tissues, including adipose tissue, express ghrelin receptor we hypothesized that ghrelin may directly affect energy metabolism in adipocytes. We have exciting new preliminary data which shows that treatment of premature 3T3-L1 adipocytes with ghrelin impairs adipocyte differentiation and inhibits lipid accumulation in the tissue designed to store energy in the form of fat. We further observed that ghrelin treatment of differentiated adipocytes significantly inhibited secretion of adiponectin, a hepatoprotective hormone that reduces lipid synthesis and promotes lipid oxidation. These results were corroborated by our observations of a significant increase in serum adiponectin levels in ethanol-fed rats treated with a ghrelin receptor antagonist verses the un-treated ethanol-fed rats. Interestingly, in adipocytes, ghrelin also increases secretion of interleukin-6 (IL-6) and CCL2 (chemokine [C–C motif] ligand 2), cytokines which promote hepatic inflammation and progression of liver disease. To summarize, the alcohol-induced increase in serum ghrelin levels dysregulates adipose-liver interaction and promotes hepatic steatosis by increasing the free fatty acid released from adipose for hepatic uptake, and by altering adiponectin and cytokine secretion. Taken together, our data indicates that targeting the activity of ghrelin may be a powerful treatment strategy.

TGF\u03b22-induced formation of lipid droplets supports acidosis-driven EMT and the metastatic spreading of cancer cells

Acidosis, a common characteristic of the tumor microenvironment, is associated with alterations in metabolic preferences of cancer cells and progression of the disease. Here we identify the TGF-β2 isoform at the interface between these observations. We document that acidic pH promotes autocrine TGF-β2 signaling, which in turn favors the formation of lipid droplets (LD) that represent energy stores readily available to support anoikis resistance and cancer cell invasiveness. We find that, in cancer cells of various origins, acidosis-induced TGF-β2 activation promotes both partial epithelial-to-mesenchymal transition (EMT) and fatty acid metabolism, the latter supporting Smad2 acetylation. We show that upon TGF-β2 stimulation, PKC-zeta-mediated translocation of CD36 facilitates the uptake of fatty acids that are either stored as triglycerides in LD through DGAT1 or oxidized to generate ATP to fulfill immediate cellular needs. We also address how, by preventing fatty acid mobilization from LD, distant metastatic spreading may be inhibited.

Decreased PEDF Promotes Hepatic Fatty Acid Uptake and Lipid Droplet Formation in the Pathogenesis of NAFLD.

Non-alcoholic fatty liver disease (NAFLD), the leading cause of chronic liver diseases worldwide, ranges from simple steatosis to steatohepatitis, with the risk for progressive fibrosis or even cirrhosis. While simple steatosis is a relatively benign condition, the buildup of toxic lipid metabolites can induce chronic inflammation, ultimately triggering disease progression. Pigment epithelium-derived factor (PEDF) is a secreted, multifunctional glycoprotein with lipid metabolic activities. PEDF promotes lipolysis through binding to adipose triglyceride lipase (ATGL), a key enzyme for triglyceride breakdown. In the current study, we aimed to delineate how changes in PEDF expression affect hepatic lipid accumulation. Our data revealed that hepatic PEDF was downregulated in a mouse NAFLD model. We further showed that decreased PEDF levels in hepatocytes in vitro resulted in elevated fatty acid uptake and lipid droplet formation, with concomitant upregulation of fatty acid transport proteins CD36 and fatty acid binding protein 1 (FABP1). RNA sequencing analysis of PEDF knocked down hepatocytes revealed an alteration in gene expression profile toward lipid accumulation. Additionally, decreased PEDF promotes mobilization of fatty acids, an observation distinct from blocking ATGL activity. Taken together, our data suggest that hepatic PEDF downregulation causes molecular changes that favor triglyceride accumulation, which may further lead to NAFLD progression.

A Non-canonical Function of BMAL1 Metabolically Limits Obesity-Promoted Triple-Negative Breast Cancer.

SummaryThe epidemiological association between disrupted circadian rhythms and metabolic diseases is implicated in increased risk of human breast cancer and poor therapeutic outcomes. To define a metabolic phenotype and the underlying molecular mechanism, we applied chronic insulin treatment (CIT) to an in vitro model of triple-negative breast cancer to directly address how BMAL1, a key circadian transcription factor, regulates cancer cell respiration and governs tumor progression. At the cellular level, BMAL1 suppresses the flexibility of mitochondrial substrate usage and the pyruvate-dependent mitochondrial respiration induced by CIT. We established an animal model of diet-induced obesity/hyperinsulinemia and observed that BMAL1 functions as a tumor suppressor in obese, but not lean, mice. Downregulation of BMAL1 is associated with higher risk of metastasis in human breast tumors. In summary, loss of BMAL1 in tumors confers advantages to cancer cells in both intrinsic mitochondrial metabolism and extrinsic inflammatory tumor microenvironment during pre-diabetic obesity/hyperinsulinemia.

Prediction and Structural Comparison of Deleterious Coding Nonsynonymous Single Nucleotide Polymorphisms (nsSNPs) in Human LEP Gene Associated with Obesity.

Leptin is a peptide hormone that regulates fat stores in the body and appetite by controlling the feeling of satiety. This hormone is secreted by the white adipose tissue and plays a role in the storage and mobilization of fatty acids. Mutations of the LEP gene have been associated with obesity in different populations; it is a multifactorial disease that constitutes a major public health problem. In this study, we evaluated the impact of missense SNPs in the LEP gene extracted from dbSNP using 8 computational prediction tools. Out of the total of 4337 SNPs, 93 were nsSNPs (nonsynonymous single nucleotide polymorphisms). Among 93 nsSNPs, 12 (S46L, G59S, D61N, D100N, N103K, C117S, D76V, S88C, P90R, I95N, L161R, and R105W) variants were predicted to be the most deleterious by prediction software. On these 12 deleterious SNPs, 8 variants (S46L, G59S, D61N, D100N, N103K, C117S, L161R, and R105W) were located in the conserved positions and showed a decrease in structure stability which was evaluated by I-Mutant and Mupro. Then, by analyzing the different interactions between different amino acids in wild and mutated proteins, we assessed the structural impact of the deleterious modifications using the YASARA software. Among 8 deleterious nsSNPs, we revealed structure changes in the 6 variants S46L, G59S, D100N, L103K, R105W, L161R, two of which R105W, N103K were previously reported as associated with obesity. Our study suggests 6 deleterious mutations could play an important role in contributing to human obesity and worth to be included in association and functional studies, then may be a drug target.

Influence of Aging and Menstrual Status on Subcutaneous Fat Cell Lipolysis.

Aging is accompanied by inhibited fat cell mobilization of fatty acids through lipolysis, which may contribute to decreased energy expenditure in elderly subjects. However, the influence of menstrual status is unknown. To investigate the role of menstrual status on changes in lipolysis induced by aging. A longitudinal investigation with a mean 13-year interval. Ambulatory study at a clinical academic unit. Eighty-two continuously recruited women between 24 and 62 years of age and with body mass index 21 to 48 kg/m2 at first examination. Twenty-nine women continued to have normal menstruation, 42 developed irregular menstruation/menopause, and 11 had a perimenstrual/menopausal phenotype already at the first examination. Lipolysis measured as glycerol release from isolated subcutaneous fat cells incubated in vitro. On average, body weight/body fat mass levels did not change over time. In all 3 groups, aging was associated with a similar decrease in spontaneous (basal) and catecholamine-stimulated lipolysis. The latter was due to decreased signal transduction through stimulatory beta adrenoceptors and increased alpha-2-adrenoceptor-mediated antilipolytic effects. Gene microarray data from adipose tissue at baseline and follow-up (n = 53) showed that a limited set of lipolysis-linked genes, including phosphodiesterase-3B, were altered over time, but this was independent of menstrual status. Fat cell size also decreased during aging, but this could not explain the decrease in lipolysis. In women, the rate of fat cell lipolysis decreases during aging due to multiple alterations in spontaneous (basal) and catecholamine-induced lipolysis. This is independent of changes in menstrual status or fat cell size.

Sodium fluorocitrate having inhibitory effect on fatty acid uptake ameliorates high fat diet-induced non-alcoholic fatty liver disease in C57BL/6J mice

Non-alcoholic fatty liver disease (NAFLD) is excessive fat build-up in the liver without alcohol consumption and includes hepatic inflammation and damage. Excessive influx of fatty acids to liver from circulation is thought to be a pathogenic cause for the development of NAFLD. Thus, inhibition of fatty acid intake into hepatocyte would be a maneuver for protection from high fat diet (HFD)-induced NAFLD. This study was initiated to determine whether sodium fluorocitrate (SFC) as a fatty acid uptake inhibitor could prevent palmitate-induced lipotoxicity in hepatocytes and protect the mice from HFD-induced NAFLD. SFC significantly inhibited the cellular uptake of palmitate in HepG2 hepatocytes, and thus prevented palmitate-induced fat accumulation and death in these cells. Single treatment with SFC reduced fasting-induced hepatic steatosis in C57BL/6J mice. Concurrent treatment with SFC for 15 weeks in HFD-fed C57BL/6J mice prevented HFD-induced fat accumulation and stress/inflammatory signal activation in the liver. SFC restored HFD-induced increased levels of serum alanine aminotransferase and aspartate aminotransferases as hepatic injury markers in these mice. SFC treatment also improved HFD-induced hepatic insulin resistance, and thus ameliorated HFD-induced hyperglycemia. In conclusion, inhibition of fatty acid mobilization into liver through SFC treatment can be a strategy to protect from HFD-induced NAFLD.

Acute hypoxia changes the mode of glucose and lipid utilization in the liver of the largemouth bass (Micropterus salmoides)

Dissolved oxygen (DO) undountedly affects fish distribution, metabolism, and evern survival. Intensive aquaculture and environmental changes will inevitably lead to hypoxic stress for largemouth bass (Micropterus salmoides). The different metabolic responses and mechanism still remains relatively unknown during acute hypoxia exposure. In this study, largemouth bass were subjected to hypoxic stress (3.0 ± 0.2 mg/L and 1.2 ± 0.2 mg/L) for 24 h and 12 h reoxygenation to systemically evaluate indicators of glucose and lipid metabolism. A regulatory network was constructed using RNA-seq to further elucidate the transcriptional regulation of glucose and lipid metabolism. During hypoxia for 4 h, the liver glycogen, glucose and pyruvic acid contents significantly decreased, whereas plasma glucose content and liver lactic acid content increased significantly. The accumulation of liver triglycerides and non-esterified fatty acids was enhanced during hypoxia for 8 h. The activity of key enzymes revealed the different metabolic responses to hypoxia exposure for 4 h, including the enhancement of glycolysis, and inhibition of gluconeogenesis. Furthermore, hypoxia exposure for 8 h increased lipid mobilization, and inhibited the β-oxidation. In addition, an integrated regulatory network of 9 major pathways involved in the response to hypoxia exposure was constructed, including HIF signaling pathway, VEGF signaling pathway, AMPK signaling pathway, insulin signaling pathway and PPAR signaling pathway; glycolysis/gluconeogenesis, pyruvate metabolism, fatty acid degradation and fatty acid biosynthesis. Additionally, reoxygenation inhibited glycolysis, and promoted gluconeogenesis and lipid oxidation, but energy deficits persisted. In short, although the mobilization and activation of fatty acid in liver were enhanced in the early stage of hypoxia, glycolysis was the main energy source under acute hypoxia. The extent and duration of hypoxia determine the degree of change in energy metabolism.