Dietary Arachidonic Acid Has a Time-Dependent Differential Impact on Adipogenesis Modulated via COX and LOX Pathways in Grass Carp Ctenopharyngodon idellus

In this study, we explored the function of arachidonic acid (ARA) in adipogenesis in the grass carp (Ctenopharyngodon idellus) using in vivo and in vitro models. An 8‐week feeding trial was performed using three isonitrogenous and isoenergetic purified diets: ARA‐free, ARA, and ARA + acetylsalicylic acid [ASA, a cyclooxygenase (COX) inhibitor]. Fish were sampled after 4 and 8 weeks of feeding. Results showed that ARA‐fed fish had a significantly lower intraperitoneal fat index (IPFI) and smaller adipocytes; these decreases were reversed by ASA after 8 weeks of feeding. Nevertheless, at week 4, the IPFI and adipocyte size were higher in the ARA group, and they were comparable to those of fish fed ARA + ASA. To further investigate the influence of ARA on adipocyte differentiation, confluent pre‐adipocytes of grass carp were incubated with ARA for 3 days. This in vitro experiment demonstrated that ARA promoted adipogenesis in a dose‐dependent manner. Pre‐treatment with the lipoxygenase (LOX) inhibitor nordihydroguaiaretic acid attenuated the pro‐adipogenic function of ARA. However, after treatment with ARA for 8 days, adipocytes had a lower lipid content than cells treated with oleic acid, and ASA could suppress this effect. We thus revealed the dual function of ARA in adipogenesis in grass carp. The LOX pathway may play a key role in pro‐adipogenesis after short‐term treatment with ARA, whereas the COX pathway is possibly responsible for the inhibition of adipogenesis after long‐term treatment.     

Cellular conditions for intramuscular fat deposition in Japanese Black and Holstein steers

The experiment was conducted to study the development of intramuscular fat in Japanese Black (JB) compared to Holstein (HS) steers and to find breed differences for fat depot development and distribution in the carcass under equal feeding conditions. Additional to slaughter samples, biopsy samples of longissimus muscle (LM) and subcutaneous fat, taken at 10, 14, 18, and 22 months of age, were used for histological and molecular investigations. Japanese Black steers stored about 14% more fat in the LM (P = 0.001), resulting in larger marbling flecks (P < 0.001). Muscle fibers and intramuscular adipocytes in both breeds responded to the high energy feeding with significant enlargement, which was faster in JB. Histograms of intramuscular adipocytes size showed a shift toward larger cells during growth, but also the abundance of small, developing adipocytes. This development was accompanied by a correlated up-regulation of adipogenic genes until 22 months of age.     

Effect of a Seaweed Extract on Fatty Acid Accumulation and Glycerol-3-Phosphate Dehydrogenase Activity in 3T3-L1 Adipocytes

This study was to determine the effect of a seaweed Ascophyllum nodosum extract (SE) containing 220 mg g⁻¹ phlorotannins on differentiation and fatty acid accumulation in differentiating 3T3-L1 adipocytes. 3T3-L1 cells (2 × 10⁴ mL⁻¹) were seeded to 24-well plates and proliferated to reach confluence and then were treated with media containing 0, 12.5, 25, 50, 75 and 100 μg mL⁻¹ SE for 8 days. Dexamethasone, methyl-isobutylxanthine and insulin (DMI) were added to the media in the first 2 days to induce cell differentiation. On day 8 the adipocytes were harvested for measuring cellular fatty acid concentration and the activity of glycerol-3-phosphate dehydrogenase (GPDH). It was found that treatment with SE increased (P < 0.01, n = 6) cellular myristoleic acid (C14:1), palmitoleic acid (C16:1) and oleic acid (C18:1) and total monounsaturated fatty acids (MUFA) without significantly affecting the cell number and saturated fatty acid (SFA). Ratios of MUFA/SFA, C14:1/C14:0, C16:1/C16:0 and C18:1/C18:0 in cellular lipids increased (P < 0.05, n = 6) with the SE treatment in a dose dependent manner (P < 0.001). Treatment with 75 μg mL⁻¹ SE depressed (P < 0.05) cellular GPDH activity. The results indicate that the biological factors in the SE may be involved in differentiation and MUFA accumulation in adipocytes.     

Role of taurine in the pathogenesis of obesity

Taurine is a sulfur‐containing amino acid that is present in mammalian tissues in millimolar concentrations. Taurine is involved in a diverse array of biological and physiological functions, including bile salt conjugation, osmoregulation, membrane stabilization, calcium modulation, anti‐oxidation, and immunomodulation. The prevalence of obesity and being overweight continues to rise worldwide at an alarming rate. Obesity is associated with a higher risk of metabolic and cardiovascular diseases, cancer, and other clinical conditions. Ingestion of taurine has been shown to alleviate metabolic diseases such as hyperlipidemia, diabetes, hypertension, and obesity in animal models. A global epidemiological survey showed that 24‐h urinary taurine excretion, as a marker of dietary taurine intake, was inversely associated with BMI, blood pressure, and plasma cholesterol in humans. In addition, taurine chloramine, an endogenous product derived from activated neutrophils, has been reported to suppress obesity‐induced oxidative stress and inflammation in adipocytes. Synthetic activity and concentration of taurine in adipose tissues and plasma have been shown to decrease in humans and animals during the development of obesity, suggesting a relationship between taurine deficiency and obesity. In this review, I summarize the effects of taurine on the progression of obesity in animal models and humans. Furthermore, I discuss possible mechanisms underlying the antiobesity effects of taurine.     

Cyclopropaneoctanoic Acid 2‐Hexyl Upregulates the Expression of Genes Responsible for Lipid Synthesis and Release in Human Hepatic HepG2 Cells

Recently we have found cyclopropaneoctanoic acid 2‐hexyl (CPOA2H) in humans and demonstrated its elevated levels in patients with metabolic diseases associated with hypertriglyceridemia. However, it is still unclear whether CPOA2H may influence lipid metabolism in lipogenic tissues. To verify this, HepG2 hepatocytes and 3T3‐L1 adipocytes were cultured with various concentrations of CPOA2H, and then the expressions of genes associated with lipid metabolism were determined. Incubation with CPOA2H at concentrations found in patients with metabolic diseases enhanced the expression of hepatocyte genes associated with lipid synthesis and release, in particular, the fatty acid synthase gene (nearly 20‐fold increase in the mRNA level). In contrast, incubation with CPOA2H caused the downregulation of most adipocyte genes associated with lipid synthesis, whereas the level of leptin mRNA was increased. These findings suggest that CPOA2H may contribute to hypertriglyceridemia in patients with metabolic diseases, upregulating the expression of hepatocyte genes responsible for lipid synthesis and release.     

Effect of the genistein metabolite on leptin secretion in murine adipocytes in vitro

Soy isoflavonoids have many useful properties. However, they are metabolized in vivo, including in humans. The effect of the metabolism of soy isoflavonoids on their properties is not fully understood. We have isolated the bacterial strain SY8519, which has been shown to metabolize daidzein to O-desmethylangolensin and to produce 2-(4-hydroxyphenyl)propionic acid from genistein. According to chiral HPLC analysis, the 2-(4-hydroxyphenyl)propionic acid obtained from the bacterium was optically active. To determine the absolute stereochemistry of the microbial product, we prepared (S)-2-(4-hydroxyphenyl)propionic acid from (S)-2-phenylpropionic and concluded that the microbial product had an R-configuration by chiral HPLC analysis. We also applied the metabolite to mouse adipocytes and found that 2-HPPA was less effective at reducing leptin secretion than the parent compound genistein. Our results suggested that ‘O-desmethylangolensin-production’ attenuates the effect of soy isoflavonoids by reducing not only the activity of daidzein but also that of genistein.     

Diosgenin present in fenugreek improves glucose metabolism by promoting adipocyte differentiation and inhibiting inflammation in adipose tissues

In obesity, adipocyte hypertrophy and chronic inflammation in adipose tissues cause insulin resistance and type‐2 diabetes. Trigonella foenum‐graecum (fenugreek) can ameliorate hyperglycemia and diabetes. However, the effects of fenugreek on adipocyte size and inflammation in adipose tissues have not been demonstrated. In this study, we determined the effects of fenugreek on adipocyte size and inflammation in adipose tissues in diabetic obese KK‐Ay mice, and identified the active substance in fenugreek. Treatment of KK‐Ay mice with a high fat diet supplemented with 2% fenugreek ameliorated diabetes. Moreover, fenugreek miniaturized the adipocytes and increased the mRNA expression levels of differentiation‐related genes in adipose tissues. Fenugreek also inhibited macrophage infiltration into adipose tissues and decreased the mRNA expression levels of inflammatory genes. In addition, we identified diosgenin, a major aglycone of saponins in fenugreek to promote adipocyte differentiation and to inhibit expressions of several molecular candidates associated with inflammation in 3T3‐L1 cells. These results suggest that fenugreek ameliorated diabetes by promoting adipocyte differentiation and inhibiting inflammation in adipose tissues, and its effects are mediated by diosgenin. Fenugreek containing diosgenin may be useful for ameliorating the glucose metabolic disorder associated with obesity.     

Influence of dietary conjugated linoleic acids and vitamin E on meat quality, and adipose tissue in rabbits

Eighty New Zealand White rabbits, age 55 days, half male and half female, were randomly assigned to one of four diets in a 2×2×2 factorial arrangement. The diets contained 0% or 0.5% CLA, and 60 or 240mg/kg α-Tocopheryl acetate. Forty-eight rabbits were slaughtered at age 92 days. Growth performances and carcass weight were higher (P<0.05) in 240mg/kg of α-tocopheryl acetate-fed rabbits. Fat and CLA isomers content of Longissimus Lumborum (LL) muscle was higher (P<0.05) in CLA-fed rabbits than control. Fatty acid composition of LL muscle was modified (P<0.05) and oxidative stability was increased (P<0.001) by both dietary treatments. CLA increased (P<0.05) triglyceride, total cholesterol and glucose levels in plasma. Adipocytes in interscapular and perirenal fat in the 240mg/kg α-tocopheryl acetate and 0.5% CLA groups were larger in size but lesser in number than in 60mg/kg α-tocopheryl acetate and no CLA rabbit (P<0.01).