Fat Metabolism

Aim: Regular endurance exercise stimulates muscle metabolic capacity, but effects of very prolonged endurance exercise are largely unknown. This study examined muscle substrate availability and utilization during prolonged endurance exercise, and associated metabolic genes. Methods: Data were obtained from 11 competitors of a 4-to 5-day, almost continuous ultraendurance race (seven males, four females; age: 36 AE 11 years; cycling _ Vo 2peak : males 57.4 AE 5.9, females 48.1 AE 4.0 mL kg)1 min)1). Before and after the race muscle biopsies were obtained from vastus lateralis, respiratory gases were sampled during cycling at 25 and 50% peak aerobic power output, venous samples were obtained, and fat mass was estimated by bioimpedance under standardized conditions. Results: After the race fat mass was decreased by 1.6 AE 0.4 kg (11%; P < 0.01). Respiratory exchange ratio at the 25 and 50% workloads decreased (P < 0.01) from 0.83 AE 0.06 and 0.93 AE 0.03 before, to 0.71 AE 0.01 and 0.85 AE 0.02, respectively, after the race. Plasma fatty acids were 3.5 times higher (from 298 AE 74 to 1407 AE 118 lmol L)1 ; P < 0.01). Muscle glycogen content fell 50% (from 554 AE 28 to 270 AE 25 nmol kg)1 d.w.; n ¼ 7, P < 0.01), whereas the decline in muscle triacylglycerol (from 32 AE 5 to 22 AE 3 mmol kg)1 d.w.; P ¼ 0.14) was not statistically significant. After the race, muscle mRNA content of lipoprotein lipase and glycogen synthase increased (P < 0.05) 3.9-and 1.7-fold, respectively, while forkhead homolog in rhabdomyosarcoma, pyruvate dehydrogenase kinase 4 and vascular endothelial growth factor mRNA tended (P < 0.10) to be higher, whereas muscle peroxisome proliferator-activated receptor c co-activator-1b mRNA tended to be lower (P ¼ 0.06). Conclusion: Very prolonged exercise markedly increases plasma fatty acid availability and fat utilization during exercise. Exercise-induced regulation of genes encoding proteins involved in fatty acid recruitment and oxidation may contribute to these changes.

Using data from the Third National Health and Nutrition Examination Survey (NHANES III), conducted from 1988-1994, we investigated the effect of reproduction on the distribution of body fat in well-nourished American women. While women tend to gain weight and fat with succeeding pregnancies, if age and body mass index are controlled, increasing parity is associated with a decrease in hip and thigh circumferences, suprailiac and thigh skinfolds, and body fat estimated from skinfolds, while waist circumference increases, resulting in a relative decrease in lowerbody fat. The mobilization of fat stores in the lower body during late pregnancy and lactation may help to meet the special needs of the developing brain for essential fatty acids and energy during the time of peak growth. When fat is regained after the postpartum period, relatively more is stored in central vs. peripheral depots, resulting in a patterned change in body shape with parity.

Taurine (2 amino ethane sulfonic acid), is a semi-essential amino acid and an end product of the sulfur amino acid metabolism. The aim of this study was improving Rosy barb (Pethia conchonius) pigmentation. The fish (average weight 32 ± 7 mg and length 12.83 ± 1.82 mm) were divided into five different groups including control (basic diet without taurine and astaxanthin) and four different levels of taurine (0, 100, 250 & 500 mg/kg diet) with constant amount of astaxanthin (100 mg/kg diet) and fed for 60 days. The pigmentation analysis was done using digital camera photography and whole body biochemical carotenoid analysis and showed that the fish fed on 100 + 250 mg/kg of astaxanthin & taurine respectively had the highest levels of pigmentation. Adding taurine up to 250 (mg/kg diet) caused increasing total carcasses lipid, plasma triglyceride, cholesterol, LDL & HDL levels in compression to the fish fed on control diet (p<0.05). It could be concluded that dietary taurine supplementation could affect fish lipid metabolism and improve astaxanthin absorption, which lead to better pigmentation in Rosy barb.

Background. The lipid metabolism is essential for maintaining the body's energy responses. Laser photobiomodulation triggers many important cellular effects, but these effects on lipid metabolism are not well described. In this study, we analyzed the laser photobiomodulation in the Lipase Sensitive Hormone activity, a key enzyme in the triglycerides hydrolysis in adipose tissue. 3T3-L1 Methods. Cells were submitted to the differentiation protocol in adipose cells, irradiated with 1J, 2J and 3J with laser (904 nm - 60 mw - laser diode) and incubated for 4 hours after irradiation. Results. The response of laser photobiomodulation was able to trigger an inhibition of Hormone-Sensitive Lipase activity (control = 0,057 ± 0,0008; 1J = 0,050 ± 0,0003; 2J = 0,0477 ± 0,002; 3J = 0,051 ± 0,002. p = 0,0003 against the control), but no modulations was observed in triglycerides levels into the medium (control =26,5856 ± 0,52; 1J = 26,5856 ± 0,52; 2J = 27,2372 ± 1,41; 3J = 25,9991 ± 0,1303, p = 0,18). Conclusion. This is the first describe of Hormone-Sensitive Lipase activity modulation with laser radiation, suggesting that photobiomodulation can influence adipose tissue metabolism and open a new field of study.

It is well established that birds use fat stores to primarily fuel migration; however, few studies have focused on the causes and consequences of observed seasonal changes in fatty acid composition of fat stores in birds. We propose and test two hypotheses that address the causes of these seasonal changes in composition of fat stores: (1) diet composition determines fatty acid composition of fat stores, and (2) birds selectively metabolize and store certain fatty acids during migration in lieu of changing their diet. When we offered Red-eyed Vireos (Vireo olivaceous) choices between diets that differed only in fatty acid composition, vireos preferred diets with more triolein over diets with more tristearin and tripalmitin, and these preferences were similar between seasons. We also collected fat samples six times throughout the year from captive Red-eyed Vireos fed one of two diets differing in fatty acid composition, and found that fatty acid composition of stored fat differed by diet and changed over time, although these changes were not season-specific or consistent with the selective-metabolism hypothesis. Thus, fatty acid composition of stored fat was primarily a product of diet composition; selective metabolism possibly played a minor, but important, role. Given recent evidence that fatty acid composition of birds affects their energy expenditure during intense exercise, the implication is that birds at stopover sites can influence the fatty acid composition of their body fat by selective feeding, and this can significantly affect the energetic cost of migration.

We examined the effects of exercise intensity and training on rates of lipolysis, plasma free fatty acid (FFA) appearance (Ra), disappearance (Rd), reesterification (Rs), and oxidation (RoxP) in postmenopausal (PM) women. Ten sedentary but healthy women (55 ± 0.6 yr) completed 12 wk of supervised endurance exercise training on a cycle ergometer [5 days/wk, 1 h/day, 65% peak oxygen consumption (V̇o2peak)]. Flux rates were determined by continuous infusion of [1-13C]palmitate and [1,1,2,3,3-2H5]glycerol during 90 min of rest and 60 min of cycle ergometer exercise during one pretraining exercise trial [65% V̇o2peak (PRE)] and two posttraining exercise trials [at power outputs that elicited 65% pretraining V̇o2peak (absolute training; ABT) and 65% posttraining V̇o2peak (relative training; RLT)]. Initial body weights (68.2 ± 4.5 kg) were maintained over the course of study. Training increased V̇o2peak by 16.3 ± 3.9% ( P &lt; 0.05) (Zarins ZA, Wallis GA, Faghihnia N, Johnson ML, Fattor JA...

The obesity epidemic has led to an increased incidence of nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes. AMP-activated protein kinase (Ampk) regulates energy homeostasis and is activated by cellular stress, hormones and the widely prescribed type 2 diabetes drug metformin 1,2 . Ampk phosphorylates mouse acetyl-CoA carboxylase 1 (Acc1; refs. 3,4) at Ser79 and Acc2 at Ser212, inhibiting the conversion of acetyl-CoA to malonyl-CoA. The latter metabolite is a precursor in fatty acid synthesis 5 and an allosteric inhibitor of fatty acid transport into mitochondria for oxidation 6 . To test the physiological impact of these phosphorylation events, we generated mice with alanine knock-in mutations in both Acc1 (at Ser79) and Acc2 (at Ser212) (Acc double knock-in, AccDKI). Compared to wild-type mice, these mice have elevated lipogenesis and lower fatty acid oxidation, which contribute to the progression of insulin resistance, glucose intolerance and NAFLD, but not obesity. Notably, AccDKI mice made obese by high-fat feeding are refractory to the lipid-lowering and insulin-sensitizing effects of metformin. These findings establish that inhibitory phosphorylation of Acc by Ampk is essential for the control of lipid metabolism and, in the setting of obesity, for metformin-induced improvements in insulin action.

Vitamin B12 deficiency is emerging as a growing public health problem. The most commonly used diagnostic tests are limited in accuracy, sensitivity, and are non-specific for B12 deficiency. The aim of this study was to develop a simple B12 breath test (BBT) to more accurately evaluate vitamin B12 status as an alternative to the most common diagnostic test, serum B12 levels. The breath test is based on the metabolism of sodium 1-13 C-propionate to 13 CO 2 which requires B12 as a cofactor. We initially compared the BBT to current B12 diagnostic methods in 58 subjects. Subjects also received a second BBT 1-3 days after initial testing to evaluate reproducibility of results. Propionate dosage, fasting times, and collection periods were compared, respectively. The dose of sodium 1-13 C-propionate (10-50 mg) gave equivalent results while an 8 h fast was essential. Statistical analysis revealed that breath collection times could be reduced to just a baseline and 10 and 20 min following propionate dosing. We also measured the incidence of B12 deficiency with the BBT in 119 patients with chronic pancreatitis, Crohn's disease, small intestinal bacterial overgrowth, and subjects over 65 years of age. The BBT results agreed with previous publications showing a higher incidence of B12 deficiency in these patients. The BBT may provide clinicians with a non-invasive, accurate, reliable, and reproducible diagnostic test to detect vitamin B12 deficiency.

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Brown adipose tissue (BAT) dissipates chemical energy in the form of heat as a defense against hypothermia and obesity. Current evidence indicates that brown adipocytes arise from Myf5 + dermotomal precursors through the action of PRDM16 (PR domain containing protein16) transcriptional complex 1,2. However, the enzymatic component of the molecular switch that determines lineage specification of brown adipocytes remains unknown. Here we show that EHMT1 (euchromatic histone-lysine N-methyltransferase 1) is an essential BAT-enriched lysine methyltransferase in the PRDM16 transcriptional complex and controls brown adipose cell fate. Loss of EHMT1 in brown adipocytes causes a severe loss of brown fat characteristics and induces muscle differentiation in vivo through demethylation of histone 3 Lys 9 (H3K9me2 and 3) of the muscle-selective gene promoters. Conversely, EHMT1 expression positively regulates the BATselective thermogenic program by stabilizing the PRDM16 protein. Notably, adipose-specific deletion of EHMT1 leads to a marked reduction of BAT-mediated adaptive thermogenesis, obesity, and systemic insulin resistance. These data indicate that EHMT1 is an essential enzymatic switch that controls brown adipose cell fate and energy homeostasis. Obesity develops when energy intake chronically exceeds total energy expenditure. All antiobesity medications currently approved by the FDA act to repress energy intake, either by suppressing appetite or by inhibiting intestinal fat absorption. However, due to their side effects including depression, oily bowel movements, and steatorrhea, there is an urgent need for alternative approaches. BAT is specialized to dissipate energy via uncoupling protein 1 (UCP1). Recent studies with 18 Fluoro-labeled 2-deoxy-glucose positron emission tomography (18 FDG-PET) scanning demonstrated that adult humans have active BAT deposits 3-6 and that its amount inversely correlate with adiposity and body mass index (BMI) 4,5 , indicating that BAT plays an important role in energy homeostasis in adult humans. Hence, a better understanding of the molecular control of BAT development may lead to an alternative approach to alter energy balance by increasing energy expenditure.

Hyperlipidemia is a risk factor for various cardiovascular and metabolic disorders. Overproduction of lipoproteins, a process that is dependent on microsomal triglyceride transfer protein (MTP), can contribute to hyperlipidemia. We show that microRNA-30c (miR-30c) interacts with the 3′ untranslated region of MTP mRNA and induces its degradation, leading to reductions in MTP activity and in apolipoprotein B (APOB) secretion. miR-30c also reduces lipid synthesis independently of MTP. Hepatic overexpression of miR-30c reduced hyperlipidemia in Western diet-fed mice by decreasing lipid synthesis and the secretion of triglyceride-rich ApoB-containing lipoproteins and decreased atherosclerosis in Apoe −/− mice. Furthermore, inhibition of hepatic miR-30c by anti-miR-30c increased hyperlipidemia and atherosclerosis. Therefore, miR-30c coordinately reduces lipid biosynthesis and lipoprotein secretion, thereby regulating hepatic and plasma lipid concentrations. Raising miR-30c levels might be useful in treating hyperlipidemias and associated disorders. npg