Metabolic fate of non-esterified fatty acids in isolated hepatocytes from newborn and young pigs. Evidence for a limited capacity for oxidation and increased capacity for esterification

In hepatocytes isolated from 48 h-old starved of suckling newborn pigs or from 15-day-old starved piglets, the rate of ketogenesis from oleate or from octanoate is very low. This is not due to an inappropriate fatty acid uptake by the isolated liver cells, but results from a limited capacity for fatty acid oxidation. Some 80-95% of oleate taken up is converted into esterified fats, whatever the age or the nutritional conditions. Three lines of indirect evidences suggest that fatty acid oxidation is not controlled primarily by malonyl-CoA concentration in newborn pig liver. Firstly, the addition of glucagon does not increase fatty acid oxidation or ketogenesis. Secondly, the rate of lipogenesis is very low in isolated hepatocytes from newborn pigs. Thirdly, the rates of oxidation and ketogenesis from octanoate are also decreased in isolated hepatocytes from newborn and young piglets. The huge rate of esterification of fatty acids in the liver of the newborn pigs probably represents a species-specific difference in intrahepatic fatty acid metabolism.

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A new leptin-mediated mechanism for stimulating fatty acid oxidation: a pivotal role for sarcolemmal FAT/CD36

Biochemical Journal ◽

10.1042/bcj20160804 ◽

2016 ◽

Vol 474 (1) ◽

pp. 149-162 ◽

Cited By ~ 11

Author(s):

Iman Momken ◽

Adrian Chabowski ◽

Ellen Dirkx ◽

Miranda Nabben ◽

Swati S. Jain ◽

...

Keyword(s):

Fatty Acids ◽

Plasma Membrane ◽

Fatty Acid ◽

Fatty Acid Oxidation ◽

Fatty Acid Uptake ◽

Acid Oxidation ◽

Acid Uptake ◽

Rat Cardiomyocytes ◽

Compound C ◽

Ampk Phosphorylation

Leptin stimulates fatty acid oxidation in muscle and heart; but, the mechanism by which these tissues provide additional intracellular fatty acids for their oxidation remains unknown. We examined, in isolated muscle and cardiac myocytes, whether leptin, via AMP-activated protein kinase (AMPK) activation, stimulated fatty acid translocase (FAT/CD36)-mediated fatty acid uptake to enhance fatty acid oxidation. In both mouse skeletal muscle and rat cardiomyocytes, leptin increased fatty acid oxidation, an effect that was blocked when AMPK phosphorylation was inhibited by adenine 9-β-d-arabinofuranoside or Compound C. In wild-type mice, leptin induced the translocation of FAT/CD36 to the plasma membrane and increased fatty acid uptake into giant sarcolemmal vesicles and into cardiomyocytes. In muscles of FAT/CD36-KO mice, and in cardiomyocytes in which cell surface FAT/CD36 action was blocked by sulfo-N-succinimidyl oleate, the leptin-stimulated influx of fatty acids was inhibited; concomitantly, the normal leptin-stimulated increase in fatty acid oxidation was also prevented, despite the normal leptin-induced increase in AMPK phosphorylation. Conversely, in muscle of AMPK kinase-dead mice, leptin failed to induce the translocation of FAT/CD36, along with a failure to stimulate fatty acid uptake and oxidation. Similarly, when siRNA was used to reduce AMPK in HL-1 cardiomyocytes, leptin failed to induce the translocation of FAT/CD36. Our studies have revealed a novel mechanism of leptin-induced fatty acid oxidation in muscle tissue; namely, this process is dependent on the activation of AMPK to induce the translocation of FAT/CD36 to the plasma membrane, thereby stimulating fatty acid uptake. Without increasing this leptin-stimulated, FAT/CD36-dependent fatty acid uptake process, leptin-stimulated AMPK phosphorylation does not enhance fatty acid oxidation.

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Isotope tracer measures of meal fatty acid metabolism: reproducibility and effects of the menstrual cycle

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00340.2004 ◽

2005 ◽

Vol 288 (3) ◽

pp. E547-E555 ◽

Cited By ~ 44

Author(s):

Ana Paola Uranga ◽

James Levine ◽

Michael Jensen

Keyword(s):

Fatty Acids ◽

Adipose Tissue ◽

Fatty Acid ◽

Menstrual Cycle ◽

Dietary Fat ◽

Fatty Acid Uptake ◽

Upper Body ◽

Acid Oxidation ◽

Acid Uptake ◽

Lower Body

Oxidation and adipose tissue uptake of dietary fat can be measured by adding fatty acid tracers to meals. These studies were conducted to measure between-study variability of these types of experiments and assess whether dietary fatty acids are handled differently in the follicular vs. luteal phase of the menstrual cycle. Healthy normal-weight men ( n = 12) and women ( n = 12) participated in these studies, which were block randomized to control for study order, isotope ([3H]triolein vs. [14C]triolein), and menstrual cycle. Energy expenditure (indirect calorimetry), meal fatty acid oxidation, and meal fatty acid uptake into upper body and lower body subcutaneous fat (biopsies) 24 h after the experimental meal were measured. A greater portion of meal fatty acids was stored in upper body subcutaneous adipose tissue (24 ± 2 vs. 16 ± 2%, P < 0.005) and lower body fat (12 ± 1 vs. 7 ± 1%, P < 0.005) in women than in men. Meal fatty acid oxidation (3H2O generation) was greater in men than in women (52 ± 3 vs. 45 ± 2%, P = 0.04). Leg adipose tissue uptake of meal fatty acids was 15 ± 2% in the follicular phase of the menstrual cycle and 10 ± 1% in the luteal phase ( P = NS). Variance in meal fatty acid uptake was somewhat ( P = NS) greater in women than in men, although menstrual cycle factors did not contribute significantly. We conclude that leg uptake of dietary fat is slightly more variable in women than in men, but that there are no major effects of menstrual cycle on meal fatty acid disposal.

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Excess body fat in men decreases plasma fatty acid availability and oxidation during endurance exercise

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00301.2003 ◽

2004 ◽

Vol 286 (3) ◽

pp. E354-E362 ◽

Cited By ~ 37

Author(s):

Bettina Mittendorfer ◽

David A. Fields ◽

Samuel Klein

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Fatty Acid Oxidation ◽

Body Fat ◽

Fat Mass ◽

Total Fatty Acid ◽

Acid Oxidation ◽

Acid Uptake ◽

Plasma Fatty Acids ◽

Exercise Induced

The effect of relative body fat mass on exercise-induced stimulation of lipolysis and fatty acid oxidation was evaluated in 15 untrained men (5 lean, 5 overweight, and 5 obese with body mass indexes of 21 ± 1, 27 ± 1, and 34 ± 1 kg/m2, respectively, and %body fat ranging from 12 to 32%). Palmitate and glycerol kinetics and substrate oxidation were assessed during 90 min of cycling at 50% peak aerobic capacity (V̇o2 peak) by use of stable isotope-labeled tracer infusion and indirect calorimetry. An inverse relationship was found between %body fat and exercise-induced increase in glycerol appearance rate relative to fat mass ( r2 = 0.74; P < 0.01). The increase in total fatty acid uptake during exercise [(μmol/kg fat-free mass) × 90 min] was ∼50% smaller in obese (181 ± 70; P < 0.05) and ∼35% smaller in overweight (230 ± 71; P < 0.05) than in lean (354 ± 34) men. The percentage of total fatty acid oxidation derived from systemic plasma fatty acids decreased with increasing body fat, from 49 ± 3% in lean to 39 ± 4% in obese men ( P < 0.05); conversely, the percentage of nonsystemic fatty acids, presumably derived from intramuscular and possibly plasma triglycerides, increased with increasing body fat ( P < 0.05). We conclude that the lipolytic response to exercise decreases with increasing adiposity. The blunted increase in lipolytic rate in overweight and obese men compared with lean men limits the availability of plasma fatty acids as a fuel during exercise. However, the rate of total fat oxidation was similar in all groups because of a compensatory increase in the oxidation of nonsystemic fatty acids.

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Theobromine ameliorates nonalcoholic fatty liver disease by regulating hepatic lipid metabolism via mTOR signaling pathway in vivo and in vitro

Canadian Journal of Physiology and Pharmacology ◽

10.1139/cjpp-2020-0259 ◽

2020 ◽

Author(s):

Dan Wei ◽

Shaofei Wu ◽

Jie Liu ◽

Xiaoqian Zhang ◽

Xiaoling Guan ◽

...

Keyword(s):

Fatty Acid ◽

Signaling Pathway ◽

Fatty Acid Oxidation ◽

Fatty Acid Uptake ◽

Mtor Signaling ◽

Acid Oxidation ◽

Acid Uptake ◽

Mtor Signaling Pathway

Theobromine, a methylxanthine present in cocoa, has been shown to possess many beneficial pharmacological properties such as anti-oxidative stress, anti-inflammatory property, and anti-microbial activity. In this study, we investigated the effects of theobromine on NAFLD and the possible underlying mechanisms in vivo and in vitro. The results showed that theobromine reduced body weight, fat mass and improved dyslipidemia. Theobromine decreased liver weight, mitigated liver injury, and significantly reduced hepatic TG level in mice with obesity. Histological examinations also showed hepatic steatosis was alleviated after theobromine treatment. Furthermore, theobromine reversed the elevated mRNA and protein expression of SREBP-1c, FASN, CD36, FABP4 and the suppressed expression of PPARα, CPT1a in the liver of mice with obesity, which were responsible for lipogenesis, fatty acid uptake and fatty acid oxidation respectively. In vitro, theobromine also downregulated SREBP-1c, FASN, CD36, FABP4 and upregulated PPARα, CPT1a mRNA and protein levels in hepatocytes in a dose-dependent manner, while these changes were reversed by L-Leucine, an mTOR agonist. The present study demonstrated that theobromine improved NAFLD by inhibiting lipogenesis, fatty acid uptake and promoting fatty acid oxidation in the liver and hepatocytes, which might be associated with its suppression of mTOR signaling pathway.

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Increased nonoxidative glycolysis despite continued fatty acid uptake during demand-induced myocardial ischemia

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00976.2001 ◽

2002 ◽

Vol 282 (5) ◽

pp. H1871-H1878 ◽

Cited By ~ 27

Author(s):

Margaret P. Chandler ◽

Hazel Huang ◽

Tracy A. McElfresh ◽

William C. Stanley

Keyword(s):

Fatty Acid ◽

Coronary Artery ◽

Fatty Acid Oxidation ◽

Lactate Production ◽

Fatty Acid Uptake ◽

Anterior Wall ◽

Acid Oxidation ◽

Acid Uptake ◽

Substrate Uptake ◽

Exogenous Fatty Acid

During stress, patients with coronary artery disease frequently fail to increase coronary flow and myocardial oxygen consumption (MV˙o 2) in response to a greater demand for oxygen, resulting in “demand-induced” ischemia. We tested the hypothesis that dobutamine infusion with flow restriction stimulates nonoxidative glycolysis without a change in MV˙o 2 or fatty acid uptake. Measurements were made in the anterior wall of anesthetized open-chest swine hearts ( n = 7). The left anterior descending (LAD) coronary artery flow was controlled via an extracorporeal perfusion circuit, and substrate uptake and oxidation were measured with radiotracers. Demand-induced ischemia was produced with intravenous dobutamine (15 μg · kg−1 · min−1) and 20% reduction in LAD flow for 20 min. Despite no change in MV˙o 2, there was a switch from lactate uptake (5.9 ± 3.1) to production (74.5 ± 16.3 μmol/min), glycogen depletion (66%), and increased glucose uptake (105%), but no change in anterior wall power or the index of anterior wall energy efficiency. There was no change in the rate of tracer-measured fatty acid uptake; however, exogenous fatty acid oxidation decreased by 71%. Thus demand-induced ischemia stimulated nonoxidative glycolysis and lactate production, but did not effect fatty acid uptake despite a fall in exogenous fatty acid oxidation.

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Effect of hyperglycemia-hyperinsulinemia on whole body and regional fatty acid metabolism

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1999.276.3.e427 ◽

1999 ◽

Vol 276 (3) ◽

pp. E427-E434 ◽

Cited By ~ 10

Author(s):

Labros S. Sidossis ◽

Bettina Mittendorfer ◽

David Chinkes ◽

Eric Walser ◽

Robert R. Wolfe

Keyword(s):

Fatty Acid ◽

Fatty Acid Oxidation ◽

Fatty Acid Metabolism ◽

Acid Metabolism ◽

Fatty Acid Uptake ◽

Whole Body ◽

Acid Oxidation ◽

Acid Uptake ◽

Similar Extent ◽

Body Level

The effects of combined hyperglycemia-hyperinsulinemia on whole body, splanchnic, and leg fatty acid metabolism were determined in five volunteers. Catheters were placed in a femoral artery and vein and a hepatic vein. U-13C-labeled fatty acids were infused, once in the basal state and, on a different occasion, during infusion of dextrose (clamp; arterial glucose 8.8 ± 0.5 mmol/l). Lipids and heparin were infused together with the dextrose to maintain plasma fatty acid concentrations at basal levels. Fatty acid availability in plasma and fatty acid uptake across the splanchnic region and the leg were similar during the basal and clamp experiments. Dextrose infusion decreased fatty acid oxidation by 51.8% (whole body), 47.4% (splanchnic), and 64.3% (leg). Similarly, the percent fatty acid uptake oxidized decreased at the whole body level (53 to 29%), across the splanchnic region (30 to 13%), and in the leg (48 to 22%) during the clamp. We conclude that, in healthy men, combined hyperglycemia-hyperinsulinemia inhibits fatty acid oxidation to a similar extent at the whole body level, across the leg, and across the splanchnic region, even when fatty acid availability is constant.

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Hyperglycemia-induced inhibition of splanchnic fatty acid oxidation increases hepatic triacylglycerol secretion

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1998.275.5.e798 ◽

1998 ◽

Vol 275 (5) ◽

pp. E798-E805 ◽

Cited By ~ 22

Author(s):

Labros S. Sidossis ◽

Bettina Mittendorfer ◽

Eric Walser ◽

David Chinkes ◽

Robert R. Wolfe

Keyword(s):

Fatty Acid ◽

Fatty Acid Oxidation ◽

Low Density Lipoprotein ◽

Density Lipoprotein ◽

Fatty Acid Uptake ◽

Secretion Rate ◽

Acid Oxidation ◽

Acid Uptake ◽

Hepatic Triacylglycerol

The effect of hyperglycemia (∼8 mmol/l) on splanchnic fatty acid oxidation and triacylglycerol (TG) secretion rates was investigated in five healthy men. U-13C-labeled fatty acids were infused to estimate fatty acid kinetics and oxidation across the splanchnic region, and in vivo labeled very low density lipoprotein (VLDL)-TG was infused to estimate TG secretion rate. Plasma fatty acid carbon enrichment and concentration were maintained constant by infusion of lipids and heparin in the hyperglycemia experiments. Fatty acid uptake by the splanchnic region was 1.4 ± 0.2 and 2.2 ± 0.9 μmol ⋅ kg−1⋅ min−1in the basal and clamp experiments, respectively, whereas fatty acid oxidation decreased from 0.4 ± 0.04 to 0.2 ± 0.05 μmol ⋅ kg−1⋅ min−1( P < 0.05). Hepatic TG secretion increased from 0.35 ± 0.07 μmol ⋅ kg−1⋅ min−1in the basal state to 0.53 ± 0.11 μmol ⋅ kg−1⋅ min−1after 15 h of hyperglycemia ( P< 0.05). Similarly, plasma VLDL-TG concentration increased from 0.28 ± 0.06 to 0.43 ± 0.05 mmol/l during the clamp ( P < 0.05). In summary, hyperglycemia attenuates fatty acid oxidation in the splanchnic region in human volunteers, even when fatty acid availability is constant. This adaptation results in a significant increase in the VLDL-TG secretion rate and concentration in plasma.

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Relationship between hepatic fatty acid oxidation and gluconeogenesis in the fasting neonatal pig

British Journal Of Nutrition ◽

10.1079/bjn19930106 ◽

1993 ◽

Vol 70 (1) ◽

pp. 81-91 ◽

Cited By ~ 11

Author(s):

Allan J. Lepine ◽

Malcolm Watford ◽

R. Dean BOYD ◽

Deborah A. Ross ◽

Dana M. Whitehead

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Fatty Acid Oxidation ◽

Oxidative Capacity ◽

Synthesis Rate ◽

Acid Oxidation ◽

Limiting Factor ◽

Glucose Synthesis ◽

Newborn Pigs ◽

Hepatic Fatty Acid Oxidation

Hepatocytes were isolated from sixteen fasting neonatal pigs and used in two experiments: (1) to determine the effect of various factors on the ability for hepatic oxidation of fatty acids and (2) to clarify the relationship between fatty acid oxidation and glucose synthesis. In Expt 1, newborn pigs were either fasted from birth for 24 h or allowed to suck ad lib. for 3 d followed by a 24 h fast. In the presence of pyruvate, oxidation of octanoate (2 mM) was about 30-fold greater than oleate (1 mM) regardless of age, but glucose synthesis was not enhanced beyond that observed for pyruvate alone. Inclusion of carnitine (1 mM), glucagon (100 nM) or dibutryl cAMP (50 μM) in the incubation media did not stimulate either fatty acid oxidation (octanoate or oleate) or glucose synthesis. Extending the period of fasting to 48 h (Expt 2) failed to enhance the fatty acid oxidative capacity or glucose synthesis rate. Likewise, the redox potential of the giuconeogenic substrate (lactate v. pyruvate) did not influence glucose synthesis regardless of the oxidative capacity exhibited for fatty acids. These data indicate that fatty acid oxidative capacity is not the first limiting factor to full expression of gluconeogenesis in hepatocytes isolated from fasted newborn pigs.

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