Relationship of cardiac remodeling and perfusion alteration with hepatic lipid metabolism in a prediabetic high fat high sucrose diet female rat model

BACKGROUND AND AIMS

Cardiovascular disease (CVD) is known to be linked with metabolic associated fatty liver disease and type 2 diabetes, but few studies assessed this relationship in prediabetes, especially among women, who are at greater risk of CVD. We aimed to evaluate cardiac alterations and its relationship with hepatic lipid metabolism in prediabetic female rats submitted to high-fat-high-sucrose diet (HFS).

METHODS AND RESULTS

Wistar female rats were divided into 2 groups fed for 5 months with standard or HFS diet. We analyzed cardiac morphology, function, perfusion and fibrosis by Magnetic Resonance Imaging. Hepatic lipid contents along with inflammation and lipid metabolism gene expression were assessed. Five months of HFS diet induced glucose intolerance (p < 0.05), cardiac remodeling characterized by increased left-ventricular volume, wall thickness and mass (p < 0.05). No significant differences were found in left-ventricular ejection fraction and cardiac fibrosis but increased myocardial perfusion (p < 0.01) and reduced cardiac index (p < 0.05) were shown. HFS diet induced hepatic lipid accumulation with increased total lipid mass (p < 0.001) and triglyceride contents (p < 0.05), but also increased mitochondrial (CPT1a, MCAD; (p < 0.001; p < 0.05) and peroxisomal (ACO, LCAD; (p < 0.05; p < 0.001) β-oxidation gene expression. Myocardial wall thickness and perfusion were correlated with hepatic β-oxidation genes expression. Furthermore, myocardial perfusion was also correlated with hepatic lipid content and glucose intolerance.

CONCLUSION

This study brings new insights on the relationship between cardiac sub-clinical alterations and hepatic metabolism in female prediabetic rats. Further studies are warranted to explore its involvement in the higher CVD risk observed among prediabetic women.

Expression enhancement in brown adipose tissue of genes related to thermogenesis and mitochondrial dynamics after administration of pepsin egg white hydrolysate

Pepsin egg white hydrolysate enhanced mitochondria proliferation on brown adipose tissue and thermogenesis. Reduced body weight and adiposity were observed.

Dietary regulation of adiponectin by direct and indirect lipid activators of nuclear hormone receptors

Adiponectin is an adipokine mainly secreted by adipocytes that presents antidiabetic, anti-inflammatory, and antiatherogenic functions. Therefore, modulation of adiponectin expression represents a promising target for prevention or treatment of several diseases including insulin resistance and type II diabetes. Pharmacological agents such as the nuclear hormone receptor synthetic agonists like peroxisome proliferator activated receptor γ agonists are of particular interest in therapeutic strategies due to their ability to increase the plasma adiponectin concentration. Nutritional approaches are also of particular interest, especially in primary prevention, since some active compounds of our diet (notably vitamins, carotenoids, or other essential nutrients) are direct or indirect lipid-activators of nuclear hormone receptors and are modifiers of adiponectin expression and secretion. The aim of the present review is to summarize current knowledge about the nutritional regulation of adiponectin by derivatives of active compounds naturally present in the diet acting as indirect or direct activators of nuclear hormone receptors.

Independent positive association of plasma β-carotene concentrations with adiponectin among non-diabetic obese subjects

PURPOSE

Many epidemiological studies find an inverse correlation between carotenoids intake or carotenoids plasma concentrations and body mass index (BMI), insulin resistance or metabolic syndrome in the general population. However, it is not clear whether these relationships occur in obese population.

METHODS

We conducted a cross-sectional study in 108 obese non-diabetic patients.

RESULTS

There was an inverse correlation between plasma levels of pro-vitamin A carotenoids (α-carotene, β-carotene and β-cryptoxanthin) and both BMI and insulin resistance (estimated by the HOMA-IR). No correlation between plasma concentrations of lycopene or lutein/zeaxanthin and BMI or insulin resistance was found. The inverse association between the three pro-vitamin A carotenoids and HOMA-IR disappeared after adjustment for BMI and waist circumference. Interestingly, we identified a positive association between concentrations of β-carotene and adiponectin in plasma that was independent of sex, age, smoking status, BMI and waist circumference. To our knowledge, such association has never been described in obese patients.

CONCLUSION

These results suggest the existence of a favourable effect of β-carotene on insulin sensitivity in obese individuals that could involve a positive regulation of adiponectin, either directly or via its pro-vitamin A activity. The demonstration of the potential benefits of β-carotene towards insulin sensitivity would open the way to dietary strategies to prevent metabolic syndrome.

Apo-10'-lycopenoic acid impacts adipose tissue biology via the retinoic acid receptors

Apo-10'-lycopenoic acid (apo-10-lycac), a metabolite of lycopene, has been shown to possess potent biological activities, notably via the retinoic acid receptors (RAR). In the current study, its impact on adipose tissue and adipocytes was studied. In microarray experiments, the set of genes regulated by apo-10-lycac treatments was compared to the set of genes regulated by all-trans retinoic acid (ATRA), the natural ligand of RAR, in adipocytes. Approximately 27.5% of the genes regulated by apo-10-lycac treatments were also regulated by ATRA, suggesting a common ability in terms of gene expression modulation, possibly via RAR transactivation. The physiological impact of apo-10-lycac on adipose tissue biology was evaluated. If it had no effect on adipogenesis in the 3T3-L1 cell model, this metabolite may have a preventative effect against inflammation, by preventing the increase in the inflammatory markers, interleukin 6 and interleukin 1β in various dedicated models. The ability of apo-10-lycac to transactivate the RAR and to modulate the transcription of RAR target gene was brought in vivo in adipose tissue. While apo-10-lycac was not detected in adipose tissue, a metabolite with a molecular weight with 2Da larger mass was detected, suggesting that a dihydro-apo-10'-lycopenoic acid, may be present in adipose tissue and that this compound could active or may lead to further active RAR-activating apo-10-lycac metabolites. Since apo-10-lycac treatments induce anti-inflammatory effects in adipose tissue but do not inhibit adipogenesis, we propose that apo-10-lycac treatments and its potential active metabolites in WAT may be considered for prevention strategies relevant for obesity-associated pathologies.

The gene encoding the human ileal bile acid-binding protein (I-BABP) is regulated by peroxisome proliferator-activated receptors

Peroxisome proliferator-activator receptors (PPAR) are involved in cholesterol homeostasis through the regulation of bile acids synthesis, composition, and reclamation. As ileal bile acid-binding protein (I-BABP) is thought to play a crucial role in the enterohepatic circulation of bile acids, we investigated whether I-BABP gene expression could also be affected by PPAR. Indeed, treatment with the PPARalpha-PPARbeta/delta agonist bezafibrate led to the up-regulation of I-BABP mRNA levels in the human intestine-derived Caco-2 cells. Cotransfections of the reporter-linked human I-BABP promoter (hI-BABP-2769/+44) together with PPAR and RXR expression vectors demonstrated that the fibrate-mediated induction of the I-BABP gene is dependent on PPARalpha or PPARbeta/delta. Using progressive 5' deletions of the hI-BABP promoter and sequence analysis, we identified a putative PPAR-binding site located at the position -198 and -186 upstream of the transcription initiation site. Electrophoretic mobility shift assays showed that the PPAR/RXR heterodimer can specifically bind to this PPRE-like motif. The deletion of the PPRE within the hI-BABP promoter abolished the PPAR-mediated transactivation in transient transfection assays. The regulation of the I-BABP promoter by PPAR appears species-specific, as the mouse I-BABP promoter, which lacks a conserved PPRE, was not responsive to exogenous PPAR expression in the presence of bezafibrate. Our findings show that the I-BABP gene may be a novel target for PPAR in humans and further emphasize the role for PPAR in the control of bile acid homeostasis.