Genetic architecture of tipburn resistance in lettuce.

KEY MESSAGE: Two major QTLs for tipburn were identified in LGs 1 and 5 contributing to resistance in cv. Salinas. The findings suggest pleiotropic effects between leaf crinkliness/savoy and tipburn. Tipburn is a physiological disorder in lettuce that is thought to be caused by a localized deficiency of calcium in leaf tissues. To elucidate the genetic architecture of resistance to tipburn in lettuce, seven recombinant inbred line populations were analyzed in multiple environments and years to identify quantitative trait loci (QTLs) for tipburn. Core height, head firmness, head closure, leaf crinkliness, plant fresh weight, and leaf savoy were also analyzed to investigate whether QTLs for these morphological traits collocated with QTLs for tipburn, which would be indicative of pleiotropic effects. Twenty-three major, intermediate, and minor unique QTLs for tipburn were identified in one or more populations scattered throughout the genome. Two major QTLs for tipburn incidence were identified in linkage groups (LGs) 1 and 5, which determined up to 45 and 66% of the phenotypic variance. The major QTL in LG 1 collocated with the head firmness QTL. The major QTL in LG 5 collocated with the QTL for core height, leaf crinkliness, and head firmness. Further research is needed to determine whether these associations are due to pleiotropic effects of the same gene or if the genes determining these traits are tightly linked. The beneficial alleles at the QTLs in LGs 1 and 5 are present in Lactuca sativa cv. Salinas, the genotype sequenced for the reference genome assembly. Therefore, these QTLs are good targets to identify genes causing tipburn as well as regions for marker-assisted selection to improve resistance to tipburn in lettuce.

Plasma FGF21 levels in obese patients undergoing energy-restricted diets or bariatric surgery: a marker of metabolic stress?

BACKGROUND: Fibroblast growth factor 21 (FGF21) has been suggested to be an endocrine signal of nutritional status and an active regulator of metabolism. However, there is no agreement on the effect of weight-loss therapies on circulating levels of FGF21 in humans. OBJECTIVE: To assess FGF21 circulating levels in adiposity excess and after different weight-loss strategies prescribed in five different groups from four independent centers. SUBJECTS AND METHODS: Body composition, ketosis, insulin sensitivity and FGF21 were evaluated in 181 excess body weight and 14 normal-weight subjects. From the excess body weight patients, two independent groups (discovery cohort; n=20 and validation cohort; n=28) undertook a very low-calorie ketogenic (VLCK) diet, a third group followed a low-calorie (LC) diet (n=84) and other two groups underwent bariatric surgery (discovery cohort; n=24 and validation cohort; n=25). The follow-up was 4 to 6 or 12 months, respectively. RESULTS: FGF21 levels were higher in excess body weight patients than in normal-weight subjects. The energy-restriction therapy to lose weight induced a significant decrease, with respect to baseline, in circulating levels of FGF21 (VLCK: -62.5 pg ml-1 or -14.8 pg ml-1 and LC diet: -67.9 pg ml-1). There were no differences in FGF21 levels between both energy-restriction treatments. On the contrary, after bariatric surgery morbidly obese patients showed a significant increase in FGF21, especially 1 month after surgery (148.8 pg ml-1 higher than baseline). The FGF21 differential changes occur concomitantly with a non-induced ketosis situation (0.66±0.56 mm) in bariatric surgery, and an improvement in adiposity and insulin sensitivity induced by the three therapies. CONCLUSIONS: FGF21 levels were reduced after energy-restricted treatments and severely increased after bariatric surgery, independently of the weight reduction magnitude, insulin sensitivity or ketosis. Therefore, FGF21 appears to be a marker of severe nutritional stress.

Molecular effect of fenofibrate on PBMC gene transcription related to lipid metabolism in patients with metabolic syndrome.

BACKGROUND: Both fasting and postprandial hypertriglyceridaemia are considered independent risk factors for atherosclerosis. Treatment of hypertriglyceridaemia is based on fibrates, which activate the peroxisome proliferator-activated receptor alpha (PPARα). However, the metabolic pathways that activate or inhibit fibrates, and how the postprandial triglyceride levels are modified, have not yet been fully described. Accordingly, the aim of this study was to determine the feasibility of peripheral blood mononuclear cells (PBMC) to study the effects of fenofibrate in patients with the metabolic syndrome. MATERIALS AND METHODS: A fat overload was given to 50 patients before and after treatment with fenofibrate for 3 months. Anthropometric and biochemical variables as well as gene expression in PBMC were analysed. RESULTS: After treatment with fenofibrate, we observed a decrease in both baseline and postprandial (3 h after the fat overload) levels of serum triglycerides, cholesterol and uric acid and an increase in HDL cholesterol and apolipoprotein AI levels. After treatment, there was also a rise in PPARα and RXRα expression and changes in genes regulated by PPARα, both baseline and postprandial. Furthermore, in vitro experiments showed that a PPARα agonist changed the expression of genes related with lipid metabolism. CONCLUSION: Treatment with fenofibrate reduced fasting and postprandial serum triglyceride levels, possibly through a mechanism related with an increase in the expression of RXRα and PPARα, by activating the pathways involved in the uptake and degradation of triglycerides and increasing the synthesis of apolipoprotein. These results suggest that PBMC may be useful for the easy study of fenofibrate actions.

Novel Oxazolidinone-Based Peroxisome Proliferator Activated Receptor Agonists: Molecular Modeling, Synthesis, and Biological Evaluation.

A series of new peroxisome proliferator activated receptors (PPARs) chiral ligands have been designed following the accepted three-module structure comprising a polar head, linker, and hydrophobic tail. The majority of the ligands incorporate the oxazolidinone moiety as a novel polar head, and the nature of the hydrophobic tail has also been varied. Docking studies using the crystal structure of an agonist bound to the ligand binding domain of the PPARα receptor have been performed as a tool for their design. Suitable synthetic procedures have been developed, and compounds with different stereochemistries have been prepared. Evaluation of basal and ligand-induced activity proved that several compounds showed agonist activity at the PPARα receptor, thus validating the oxazolidinone template for PPAR activity. In addition, two compounds, 2 and 4, showed dual PPARα/PPARγ agonism and interesting food intake reduction in rats.

The obese healthy paradox: is inflammation the answer?

A paradoxical but common finding in the obesity clinic is the identification of individuals who can be considered 'inappropriately' healthy for their degree of obesity. We think that studying these obese but metabolically healthy individuals and comparing them with equally obese but insulin-resistant individuals could provide important insights into the mechanistic link between adipose tissue expansion and associated metabolic alterations. In the present study, we investigated whether there are differences in inflammatory and insulin signalling pathways in VAT (visceral adipose tissue) that could account for the metabolic differences exhibited by morbidly obese individuals who are either insulin-resistant (IR-MO) or paradoxically insulin-sensitive (NIR-MO). Our results indicate that there are pathways common to obesity and unrelated to insulin resistance and others that are discriminative for insulin resistance for a similar degree of obesity. For instance, all morbidly obese patients, irrespective of their insulin resistance, showed increased expression of TNFalpha (tumour necrosis factor alpha) and activation of JNK1/2 (c-Jun N-terminal kinase 1/2). However, the IR-MO group showed significantly elevated expression levels of IL (interleukin)-1beta and IL-6 and increased macrophage infiltrates compared with non-obese individuals and NIR-MO. IkappaBalpha [inhibitor of NF-kappaB (nuclear factor kappaB) alpha], the activation of ERK1/2 (extracellular-signal-regulated kinase 1/2) and NF-kappaB were discriminative of the state of insulin resistance and correlated with differential changes in IRS-1 (insulin receptor substrate 1) expression and Akt activation between IR-MO and NIR-MO individuals. Our results support the concept that NIR-MO individuals lack the inflammatory response that characterizes the IR-MO patient and that IL-6, IL-1beta, ERK and NF-kappaB are important effectors that mediate the inflammation effects promoting insulin resistance.

Obesity and insulin resistance-related changes in the expression of lipogenic and lipolytic genes in morbidly obese subjects.

BACKGROUND: The storage capacity of adipose tissue may be an important factor linking obesity, insulin resistance (IR), and associated morbidities. The aim of this study was to analyze the expression of lipogenic and lipolytic genes in adipose tissue and the influence of IR. METHODS: We studied the mRNA expression of peroxisome proliferator-activated receptor-γ (PPARγ) and lipogenic and lipolytic enzymes in the visceral (VAT) and subcutaneous adipose tissue (SAT) from 23 morbidly obese patients (MO; 13 with low IR and ten with high IR) and from 15 healthy, lean controls. RESULTS: In the VAT and SAT from the MO, we found an increased expression of PPARγ (p = 0.001 and p = 0.022, respectively), acyl-coenzyme A (CoA)/cholesterol acyltransferase (p < 0.001 and p < 0.001), aquaporin 7 (p < 0.001 and p = 0.003), and adipose triglyceride lipase (p < 0.001 and p < 0.001) and a reduced expression of acetyl-coenzyme A carboxylase (p = 0.004 and p < 0.001), independently of the state of IR. The expression of phosphoenolpyruvate carboxykinase and acyl-CoA synthetase, however, was significantly lower in the MO with high IR (p < 0.05). Glycerol kinase (p = 0.010), hormone-sensitive lipase (p < 0.001), and perilipin (p = 0.006) were only significantly increased in VAT. Acyl-CoA synthetase (p = 0.012) and fatty acid binding protein-4 (p = 0.003) were only significantly decreased in SAT. The expression of the genes studied was only greater in the SAT than the VAT in the controls. CONCLUSION: Our results show an upregulation of genes facilitating triglyceride/fatty acid cycling and a reduction in the genes involved in de novo synthesis of fatty acids in morbid obesity. The expression of some of the genes studied seems to be related with the state of IR. VAT and SAT differ metabolically and also between controls and MO.

PPARgamma2 protects against obesity by means of a mechanism that mediates insulin resistance.

BACKGROUND: Many studies have focused on the physiological parameters and genetic predisposition of subjects presenting both obesity and insulin resistance (IR) and it has been suggested that the peroxisome proliferator-activated receptor gamma 2 (PPARgamma2) Pro12Ala variant may contribute to the observed variability in insulin sensitivity. We investigated whether the PPARgamma2 mRNA expression levels are associated with IR in morbid obesity in adipose and muscle tissues. MATERIALS AND METHODS: In this study, tissue biopsies were obtained from 26 morbidly obese (MO) patients and eight controls. The MO patients were divided into two groups: those with a low homeostasis model assessment of IR (HOMA-IR < 5) (MO-nonIR) and those with a high HOMA-IR (HOMA-IR > or = 8) (MO-IR). PPARgamma1, PPARgamma2 and aP2 mRNA expression levels were measured using quantitative RT-PCR. RESULTS: The study found that PPARgamma2 mRNA expression in visceral adipose tissue (VAT) was significantly lower in the MO patients (P = 0.002) than the controls. Moreover, the PPARgamma2 mRNA expression was lower in VAT (P < 0.05) and muscle tissue (P < 0.01), and higher in subcutaneous adipose tissue (SAT) (P < 0.01) in the MO-IR than the MO-nonIR group. By contrast, PPARgamma1 mRNA expression levels were not dependent on IR. Finally, the MO patients showed a significant negative correlation between PPARgamma2 mRNA expression and IR (r = -0.396, P = 0.020) in VAT and a positive correlation in SAT (r = 0.826, P < 0.001). The variable that best explained the IR was PPARgamma2 mRNA expression in SAT (P = 0.002). CONCLUSIONS: These data show that PPARgamma2 mRNA is expressed differently in the two types of MO patients and is associated with IR.