The Metabolically Obese, Normal-Weight Phenotype in Young Rats Is Associated with Cognitive Impairment and Partially Preventable with Leptin Intake during Lactation.

The intake of high-fat diets (HFDs) and obesity are linked to cognitive impairment. Here, we aimed to investigate whether an early metabolically obese, normal-weight (MONW) phenotype, induced with an HFD in young rats, also leads to cognitive dysfunction and to evaluate the potential cognitive benefits of neonatal intake of leptin. To achieve this, Wistar rats orally received physiological doses of leptin or its vehicle during lactation, followed by 11 weeks of pair-feeding with an HFD or control diet post-weaning. Working memory was assessed using a T-maze, and gene expression in the hippocampus and peripheral blood mononuclear cells (PBMCs) was assessed with real-time RT-qPCR to identify cognition biomarkers. Young MONW-like rats showed hippocampal gene expression changes and decreased working memory. Animals receiving leptin during lactation presented similar gene expression changes but preserved working memory despite HFD intake, partly due to improved insulin sensitivity. Notably, PBMC Syn1 expression appears as an accessible biomarker of cognitive health, reflecting both the detrimental effect of HFD intake at early ages despite the absence of obesity and the positive effects of neonatal leptin treatment on cognition. Thus, the MONW phenotype developed at a young age is linked to cognitive dysfunction, which is reflected at the transcriptomic level in PBMCs. Neonatal leptin intake can partly counteract this impaired cognition resulting from early HFD consumption.

Perinatal Treatment with Leptin, but Not Celastrol, Protects from Metabolically Obese, Normal-Weight Phenotype in Rats.

Perinatal nutrition has a well-known influence on obesity susceptibility. We previously demonstrated the protective anti-obesity effects of perinatal leptin administration. Celastrol is a natural compound acting as a leptin sensitizer with anti-obesity effects when administered in adult animals. Here, we aimed to determine if perinatal treatment with leptin, celastrol, or their combination was able to improve metabolic health in animals fed an isocaloric high-fat (HF) diet. Leptin and/or celastrol or their vehicle were administered orally to rats during the suckling period. After weaning, animals were chronically pair-fed with an HF diet provided isocaloric to the intake of a normal-fat diet by control animals to avoid obesity. Isocaloric HF feeding in vehicle-treated animals resulted in metabolic features characteristic of the metabolically obese, normal-weight (MONW) phenotype, i.e., obesity-related disturbances without increased body weight. Leptin treatment prevented liver fat deposition and insulin resistance, induced greater insulin and leptin signaling capacity, decreased gene expression of orexigenic signals at the hypothalamic level, and induced browning in retroperitoneal adipose tissue. However, celastrol treatment did not provide any protective effect and resulted in greater size of the retroperitoneal adipose depot, higher circulating glucose and insulin levels, and decreased leptin sensitivity capacity in adipose tissue. The co-administration of leptin ameliorated the negative effects of celastrol on the retroperitoneal depot, inducing browning and decreasing its size. In conclusion, the perinatal administration of leptin, but not celastrol, provided protection against the consequences of dietary unbalances leading to an MONW phenotype in adulthood.

Impaired CPT1A Gene Expression Response to Retinoic Acid Treatment in Human PBMC as Predictor of Metabolic Risk.

Ex vivo human peripheral blood mononuclear cell (PBMC) systems offer the possibility to test transcriptomic effects of food bioactive compounds with potential health effects. We investigated all-trans retinoic acid (ATRA) effect on mRNA expression of key lipid metabolism and inflammatory genes in PBMCs from normal-weight (NW) and overweight-obese (OW-OB) men with different metabolic syndrome-related features. PBMCs were incubated with 10 µM ATRA and mRNA levels of selected genes were analyzed using real-time RT-qPCR. Human ex vivo PBMCs responded to ATRA treatment, but the response for some genes was dependent on body mass index (BMI), with a lower response in PBMC from OW-OB than from NW donors. Moreover, gene expression response was affected by circulating high-density lipoprotein (HDL)-cholesterol levels. Particularly, the response to ATRA of CPT1A, previously reported as a sensitive metabolic risk predictive biomarker, was dependent on HDL levels and not on BMI, being impaired in those individuals with lower HDL levels, specifically in OW-OB. Thus, PBMCs' insensitivity to ATRA, which can be considered as indicative of impaired metabolism, was observed in individuals with higher metabolic risk (OW-OB with low HDL levels). In conclusion, an ex vivo human PBMC system indicates that ATRA response could be influenced by metabolic syndrome features. Moreover, our study reinforces the role of CPT1A as a marker of metabolic risk and points to plasmatic HDL-cholesterol levels as a parameter to take into consideration when the effects of nutritional factors and/or dietary interventions on humans are under study. Further studies including women are required to detect potential gender differences in the observed effects.

A Genetic Score of Predisposition to Low-Grade Inflammation Associated with Obesity May Contribute to Discern Population at Risk for Metabolic Syndrome.

Omega-3 rich diets have been shown to improve inflammatory status. However, in an ex vivo system of human blood cells, the efficacy of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) modulating lipid metabolism and cytokine response is attenuated in overweight subjects and shows high inter-individual variability. This suggests that obesity may be exerting a synergistic effect with genetic background disturbing the anti-inflammatory potential of omega-3 long-chain polyunsaturated fatty acids (PUFA). In the present work, a genetic score aiming to explore the risk associated to low grade inflammation and obesity (LGI-Ob) has been elaborated and assessed as a tool to contribute to discern population at risk for metabolic syndrome. Pro-inflammatory gene expression and cytokine production as a response to omega-3 were associated with LGI-Ob score; and lower anti-inflammatory effect of PUFA was observed in subjects with a high genetic score. Furthermore, overweight/obese individuals showed positive correlation of both plasma C-Reactive Protein and triglyceride/HDLc-index with LGI-Ob; and high LGI-Ob score was associated with greater hypertension (p = 0.047), Type 2 diabetes (p = 0.026), and metabolic risk (p = 0.021). The study shows that genetic variation can influence inflammation and omega-3 response, and that the LGI-Ob score could be a useful tool to classify subjects at inflammatory risk and more prone to suffer metabolic syndrome and associated metabolic disturbances.

Cognitive impairment in metabolically-obese, normal-weight rats: identification of early biomarkers in peripheral blood mononuclear cells.

BACKGROUND: Metabolically-obese, normal-weight (MONW) individuals are not obese in terms of weight and height but have a number of obesity-related features (e.g. greater visceral adiposity, insulin resistance, and increased risk of cardiovascular disease). The MONW phenotype is related to the intake of unbalanced diets, such as those rich in fat. Increasing evidence shows a relationship between high-fat diet consumption and mild cognitive impairment and dementia. Thus, MONW individuals could be at a greater risk of cognitive dysfunction. We aimed to evaluate whether MONW-like animals present gene expression alterations in the hippocampus associated with an increased risk of cognitive impairment, and to identify early biomarkers of cognitive dysfunction in peripheral blood mononuclear cells (PBMC). METHODS: Wistar rats were chronically fed with a 60% (HF60) or a 45% (HF45) high-fat diet administered isocalorically to control animals to mimic MONW features. Expression analysis of cognitive decline-related genes was performed using RT-qPCR, and working memory was assessed using a T-maze. RESULTS: High-fat diet consumption altered the pattern of gene expression in the hippocampus, clearly pointing to cognitive decline, which was accompanied by a worse performance in the T-maze in HF60 animals. Remarkably, Syn1 and Sorl1 mRNA showed the same expression pattern in both the hippocampus and the PBMC obtained at different time-points in the HF60 group, even before other pathological signs were observed. CONCLUSIONS: Our results demonstrate that long-term intake of high-fat diets, even in the absence of obesity, leads to cognitive disruption that is reflected in PBMC transcriptome. Therefore, PBMC are revealed as a plausible, minimally-invasive source of early biomarkers of cognitive impairment associated with increased fat intake.

Peripheral Blood Cells, a Transcriptomic Tool in Nutrigenomic and Obesity Studies: Current State of the Art.

Gene expression profile of peripheral blood cells (PBC) is able to reflect useful aspects of the whole body metabolic status. Therefore, and favored by the huge development of "omic" technologies, blood cells and, particularly, the peripheral blood mononuclear cell (PBMC) fraction, are emerging as a potent source of transcriptomic biomarkers of health and disease. In this review we describe and discuss the available information concerning the use of the PBC and the PBMC fraction as a crucial tool for nutrigenomic studies. Results of these studies reveal, as these cells are good indicators of metabolic adaptations to diet and, moreover, as they allow us to monitor from early stages on, the metabolic alterations associated with dietary imbalances. In this way, blood cells present the capacity of reflecting higher risks of suffering from diet-related pathologies, such as obesity and its medical complications. What is more, different studies also show how PBMC are able to evidence the metabolic recovery associated with weight loss or dietary interventions. Besides, recent research points to the utility of ex vivo systems of blood cells to test the efficacy of food bioactives. All in all, PBC constitutes an easily obtainable source of predictive biomarkers of metabolic imbalance and disease related to diet and obesity, and also of metabolic recovery, which appears as highly relevant for developing nutritional preventive strategies in dietetics. Moreover, they could serve to perform relatively simple and economic in vitro tests to assess food bioactive compounds, promoting in this way functional food research and related industry developments.

Human peripheral blood mononuclear cell in vitro system to test the efficacy of food bioactive compounds: Effects of polyunsaturated fatty acids and their relation with BMI.

SCOPE: To analyse the usefulness of isolated human peripheral blood mononuclear cells (PBMC) to rapidly/easily reflect n-3 long-chain polyunsaturated fatty acid (LCPUFA) effects on lipid metabolism/inflammation gene profile, and evaluate if these effects are body mass index (BMI) dependent. METHODS AND RESULTS: PBMC from normoweight (NW) and overweight/obese (OW/OB) subjects were incubated with physiological doses of docosahexaenoic (DHA), eicosapentaenoic acid (EPA), or their combination. PBMC reflected increased beta-oxidation-like capacity (CPT1A expression) in OW/OB but only after DHA treatment. However, insensitivity to n-3 LCPUFA was evident in OW/OB for lipogenic genes: both PUFA diminished FASN and SREBP1C expression in NW, but no effect was observed for DHA in PBMC from high-BMI subjects. This insensitivity was also evident for inflammation gene profile: all treatments inhibited key inflammatory genes in NW; nevertheless, no effect was observed in OW/OB after DHA treatment, and EPA effect was impaired. SLC27A2, IL6 and TNFα PBMC expression analysis resulted especially interesting to determine obesity-related n-3 LCPUFA insensitivity. CONCLUSION: A PBMC-based human in vitro system reflects n-3 LCPUFA effects on lipid metabolism/inflammation which is impaired in OW/OB. These results confirm the utility of PBMC ex vivo systems for bioactive-compound screening to promote functional food development and to establish appropriate dietary strategies for obese population.

Peripheral blood mononuclear cells as a potential source of biomarkers to test the efficacy of weight-loss strategies.

OBJECTIVES: Peripheral blood mononuclear cells (PBMC) constitute an easily obtainable blood cell fraction useful in nutrition and obesity studies. Our aim was to study the potential use of PBMC to reflect metabolic recovery associated with weight loss in rats. METHODS: By real-time PCR, the fasting response of key energy homeostatic genes in PBMC samples of control and cafeteria-obese rats and of rats fed a control diet after the intake of a cafeteria diet (post-cafeteria model) was analyzed. RESULTS: Fasting caused decreased mRNA expression of lipogenic (Fasn and Srebp1a) and adipogenic (Pparγ) genes in PBMC, whereas it increased the expression of the key beta-oxidation gene Cpt1a and the orexigenic gene Npy. Fasting response of the genes studied was impaired in cafeteria-obese animals but was recovered in post-cafeteria rats, which showed a significant body weight decrease and normalization of adipose and metabolic parameters. Npy expression analyzed in PBMC has been revealed to be especially useful as a marker of fasting sensitivity, as its fasting response is not affected by the age of the animals and it is recovered even after shorter time of exposure to a balanced diet. CONCLUSIONS: PBMC reflect homeostatic balance recovery associated with weight loss in obese animals, when reverting from a hyperlipidic to a control balanced diet.