Berenice Palacios-González

Synthesis of long-chain polyunsaturated fatty acids in lactating mammary gland: role of Δ5 and Δ6 desaturases, SREBP-1, PPARα, and PGC-1

The purpose of this work was to study whether rat lactating mammary gland can synthesize PUFAs through the expression of Δ5 and Δ6 desaturases (Δ5D and Δ6D), whether these enzymes are regulated by the transcription factors sterol-regulatory element binding protein 1 (SREBP-1) and peroxisome proliferator-activated receptor α (PPARα) and the coactivator peroxisome proliferator-activated receptor γ coactivator 1β (PGC-1β), and whether these desaturases are regulated by the lipid concentration in the diet. The results showed that on day 12 of lactation, ∼35% of the linoleic acid in the diet, which is the precursor of PUFAs, is transferred to the mammary gland. There was expression of Δ5D and Δ6D in mammary gland, and it was regulated by the corn oil content in the diet. The higher the corn oil content in the diet, the lower the expression of both desaturases. Induction of Δ5D and Δ6D was associated positively with similar changes in SREBP-1 and PGC-1β. Expression of PPARα was barely detected and was not affected by the corn oil content in the diet, whereas PGC-1β expression increased as the corn oil in the diet increased. These results indicate that the lactating mammary gland has the capacity to synthesize PUFAs and can be regulated by the lipid content in the diet.

Irisin levels before and after physical activity among school‐age children with different BMI: A direct relation with leptin

Irisin is a novel myokine that seems to mediate the beneficial effects of exercise. Levels of circulating irisin before and after an 8‐month physical activity program (PAP) in school‐age children were evaluated.

Flavonoids and saponins extracted from black bean (Phaseolus vulgaris L.) seed coats modulate lipid metabolism and biliary cholesterol secretion in C57BL/6 mice.

Black bean (Phaseolus vulgaris L.) seed coats are a rich source of natural compounds with potential beneficial effects on human health. Beans exert hypolipidaemic activity; however, this effect has not been attributed to any particular component, and the underlying mechanisms of action and protein targets remain unknown. The aim of the present study was to identify and quantify primary saponins and flavonoids extracted from black bean seed coats, and to study their effects on lipid metabolism in primary rat hepatocytes and C57BL/6 mice. The methanol extract of black bean seed coats, characterised by a HPLC system with a UV-visible detector and an evaporative light-scattering detector and HPLC-time-of-flight/MS, contained quercetin 3-O-glucoside and soyasaponin Af as the primary flavonoid and saponin, respectively. The extract significantly reduced the expression of SREBP1c, FAS and HMGCR, and stimulated the expression of the reverse cholesterol transporters ABCG5/ABCG8 and CYP7A1 in the liver. In addition, there was an increase in the expression of hepatic PPAR-α. Consequently, there was a decrease in hepatic lipid depots and a significant increase in bile acid secretion. Furthermore, the ingestion of this extract modulated the proportion of lipids that was used as a substrate for energy generation. Thus, the results suggest that the extract of black bean seed coats may decrease hepatic lipogenesis and stimulate cholesterol excretion, in part, via bile acid synthesis.

Dietary Type and Amount of Fat Modulate Lipid Metabolism Gene Expression in Liver and in Adipose Tissue in High-fat Diet-fed Rats

BACKGROUND AND AIMS Dietary fat plays a central role in the development of obesity. However, the metabolic consequences of dietary fat can vary depending on their fatty acid composition. Therefore, the aim of the present work was to study the effect of the type and amount of dietary fat on the expression of genes controlling lipogenesis and fatty acid oxidation in the liver or adipose tissue of rats. METHODS The expression of hepatic or adipose tissue lipid metabolic genes from Sprague Dawley or Zucker(fa/fa) rats, respectively, was measured after chronic consumption of diets containing different types/amounts of dietary fats or after rats were adapted for 2 months to a high-fat Western diet and then fed different types and amounts of fats. RESULTS Each fat or oil in the diet regulated differentially the expression of transcription factors involved in lipogenesis and fatty acid oxidation as well as some of its target genes in liver. The expression of these genes after a chronic consumption of a high-fat Western diet was reestablished in the presence of less dietary fat and was dependent on the type of fat. In obese Zucker(fa/fa) rats, consumption of a high-fat diet repressed the expression of lipogenic, fatty acid oxidation and thermogenic genes in adipose tissue. CONCLUSIONS Type of fat influences the expression of genes that are involved in lipid metabolism in liver and adipose tissue, but this response is repressed when the amount of dietary fat is excessive, diminishing the differences between each type of fat.

Genistein stimulates fatty acid oxidation in a leptin receptor-independent manner through the JAK2-mediated phosphorylation and activation of AMPK in skeletal muscle

Obesity is a public health problem that contributes to the development of insulin resistance, which is associated with an excessive accumulation of lipids in skeletal muscle tissue. There is evidence that soy protein can decrease the ectopic accumulation of lipids and improves insulin sensitivity; however, it is unknown whether soy isoflavones, particularly genistein, can stimulate fatty acid oxidation in the skeletal muscle. Thus, we studied the mechanism by which genistein stimulates fatty acid oxidation in the skeletal muscle. We showed that genistein induced the expression of genes of fatty acid oxidation in the skeletal muscle of Zucker fa/fa rats and in leptin receptor (ObR)-silenced C2C12 myotubes through AMPK phosphorylation. Furthermore, the genistein-mediated AMPK phosphorylation occurred via JAK2, which was possibly activated through a mechanism that involved cAMP. Additionally, the genistein-mediated induction of fatty acid oxidation genes involved PGC1α and PPARδ. As a result, we observed that genistein increased fatty acid oxidation in both the control and silenced C2C12 myotubes, as well as a decrease in the RER in mice, suggesting that genistein can be used in strategies to decrease lipid accumulation in the skeletal muscle.

Soya protein stimulates bile acid excretion by the liver and intestine through direct and indirect pathways influenced by the presence of dietary cholesterol

Several studies using different animal models have demonstrated that the consumption of soya protein (SP) reduces serum cholesterol concentrations by increasing the excretion of bile acids (BA). However, the mechanism by which SP enhances BA excretion is not fully understood. Therefore, the aim of the present study was to determine whether the consumption of SP regulates the expression of key enzymes involved in hepatic BA synthesis and the transporters involved in reverse cholesterol transport (RCT) via fibroblast growth factor 15 (FGF15) and/or small heterodimer protein (SHP) in rats. To achieve this aim, four groups of rats were fed experimental diets containing 20 % casein (C) or SP with or without the addition of 0·2 % cholesterol and the expression of hepatic genes involved in BA synthesis and the ileal and hepatic RCT was measured. Rats fed the SP diet had higher concentrations of ileal FGF15 and hepatic FGF15 receptor (FGFR4) and increased expression of SHP and liver receptor homolog 1 (LRH1) than those fed the C diet; as a result, the excretion of faecal BA was greater. The addition of cholesterol to the diet repressed the protein abundance of FGF15 and FGFR4; however, SP increased the expression of SHP and LRH1 to a lesser extent. Nonetheless, the expression of ABCG5/8 was increased in the intestine of rats fed the SP diet, and the effect was enhanced by the addition of cholesterol to the diet. In conclusion, SP in the presence of cholesterol increases BA synthesis via the repressions of FGF15 and SHP and accelerates BA excretion to prevent cholesterol overload in the enterocytes by increasing RCT.

Recycling of glucagon receptor to plasma membrane increases in adipocytes of obese rats by soy protein; implications for glucagon resistance

SCOPE Hyperglucagonemia contributes to hyperglycemia in type 2 diabetes (T2D). Previously, we have found that soy protein normalized fasting hyperglucagonemia in obese Zucker (fa/fa) rats, sensitizing the HSL-lipolytic signaling pathway in white adipose tissue (WAT), however the mechanism remains unknown. METHODS AND RESULTS Zucker (fa/fa) rats were fed casein or soy protein diet in combination with soybean or coconut oil. Glucagon receptor (GR) was increased at the plasma membrane of adipocytes of rats fed soy protein compared to those fed casein, without changes in total GR abundance. The protein abundance of Rab4, a GTPase involved in GR fast recycling, was dramatically up-regulated in adipocytes of rats fed soy protein. The proportion of GR bound to Rab4 or to RAMP2, involved in promoting GR ligand-binding and G protein selectivity, increased when soy protein was combined with soybean oil as fat source. In rats fed soy protein with coconut oil, Rab11 levels, a protein involved in the slow recycling of GR, was also increased. CONCLUSION Soy protein increases GR recycling to the membrane of adipocytes and its ligand-binding and G protein selectivity, suggesting, it could be used in T2D dietary treatment to reestablish glucagon sensitivity in WAT, leading to the regulation of circulating glucagon levels.