High-fat diet induces emergence of brown-like adipocytes in white adipose tissue of spontaneously hypertensive rats

The Interplay of Lifestyle and Adipokines in the Non-Obese Stroke-Prone Spontaneously Hypertensive Rats

Although the morphological features and functions of adipose tissue are well-described in obesity-prone animal models, less information is available on animals such as the stroke-prone spontaneously hypertensive (SHRSP) strain with cardiovascular abnormalities, which is not characterized by excessive adiposity. Our aim was to focus on lifestyle-induced (type of diet and physical exercise) effects on adipokine profile and lipid peroxidation in SHRSP rats. In our study, male Wistar-kyoto (control) and SHRSP rats were used. SHRSP rats were fed either standard chow or a high-fat diet with 40% fat content (HFD). One group of the animals was placed into cages fitted with a running-wheel; thus, the dietary and training period started at the same time and lasted for 12 weeks. At the end of the experimental period, adiponectin, leptin, omentin, and chemerin concentrations were determined from adipose tissue and serum. Besides adipokines, malondialdehyde (MDA) levels were also measured. Twelve weeks of HFD significantly decreased adiponectin and omentin concentrations of both adipose tissue and serum, which were ameliorated by physical exercise. Serum leptin, chemerin, and MDA values were elevated in HFD groups; however, physical exercise was able to mitigate these adverse changes. Our results underpin the crosstalk between lifestyle changes and dysfunctional adipose tissue in SHRSP rats.

FTO gene expression in diet-induced obesity is downregulated by Solanum fruit supplementation

The Fat Mass and Obesity-associated (FTO) gene has been shown to play an important role in developing obesity, manifesting in traits such as increased body mass index, increased waist-to-hip ratio, and the distribution of adipose tissues, which increases the susceptibility to various metabolic syndromes. In this study, we evaluated the impact of fruit-based diets of Solanum melongena (SMF) and Solanum aethiopicum fruits (SAF) on the FTO gene expression levels in a high-fat diet (HFD)-induced obese animals. Our results showed that the mRNA level of the FTO gene was downregulated in the hypothalamus, and white and brown adipose tissue following three and six weeks of treatment with SMF- and SAF-based diets in the HFD-induced obese animals. Additionally, the Solanum fruit supplementation exhibited a curative effect on obesity-associated abrasions on the white adipose tissue (WAT), hypothalamus, and liver. Our findings collectively suggest the anti-obesity potential of SMF and SAF via the downregulation of the FTO gene.

Treatment with atrial natriuretic peptide induces adipose tissue browning and exerts thermogenic actions in vivo

Increasing evidence suggests natriuretic peptides (NPs) coordinate inter-organ metabolic crosstalk with adipose tissues and play a critical role in energy metabolism. We recently reported A-type NP (ANP) raises intracellular temperature in cultured adipocytes in a low-temperature-sensitive manner. We herein investigated whether exogenous ANP-treatment exerts a significant impact on adipose tissues in vivo. Mice fed a high-fat-diet (HFD) or normal-fat-diet (NFD) for 13 weeks were treated with or without ANP infusion subcutaneously for another 3 weeks. ANP-treatment significantly ameliorated HFD-induced insulin resistance. HFD increased brown adipose tissue (BAT) cell size with the accumulation of lipid droplets (whitening), which was suppressed by ANP-treatment (re-browning). Furthermore, HFD induced enlarged lipid droplets in inguinal white adipose tissue (iWAT), crown-like structures in epididymal WAT, and hepatic steatosis, all of which were substantially attenuated by ANP-treatment. Likewise, ANP-treatment markedly increased UCP1 expression, a specific marker of BAT, in iWAT (browning). ANP also further increased UCP1 expression in BAT with NFD. Accordingly, cold tolerance test demonstrated ANP-treated mice were tolerant to cold exposure. In summary, exogenous ANP administration ameliorates HFD-induced insulin resistance by attenuating hepatic steatosis and by inducing adipose tissue browning (activation of the adipose tissue thermogenic program), leading to in vivo thermogenesis during cold exposure.

High Choline Intake during Pregnancy Reduces Characteristics of the Metabolic Syndrome in Male Wistar Rat Offspring Fed a High Fat But Not a Normal Fat Post-Weaning Diet

Maternal choline intakes are below recommendations, potentially impairing the child’s later-life metabolic health. This study aims to elucidate the interaction between the choline content of the gestational diet (GD) and fat content of the post-weaning diet (PWD) on metabolic phenotype of male Wistar rats. Pregnant Wistar rats were fed a standard rodent diet (AIN-93G) with either recommended choline (RC, 1 g/kg diet choline bitartrate) or high choline (HC, 2.5-fold). Male pups were weaned to either a normal (16%) fat (NF) or a high (45%) fat (HF) diet for 17 weeks. Body weight, visceral adiposity, food intake, energy expenditure, plasma hormones, triglycerides, and hepatic fatty acids were measured. HC-HF offspring had 7% lower body weight but not food intake, and lower adiposity, plasma triglycerides, and insulin resistance compared to RC-HF. They also had increased hepatic n-3 fatty acids and a reduced n-6/n-3 and C 18:1 n-9/C18:0 ratios. In contrast, HC-NF offspring had 6–8% higher cumulative food intake and body weight, as well as increased leptin and elevated hepatic C16:1 n-7/C16:0 ratio compared to RC-NF. Therefore, gestational choline supplementation associated with improved long-term regulation of several biomarkers of the metabolic syndrome in male Wistar rat offspring fed a HF, but not a NF, PWD.

Maternal Choline Intake Programs Hypothalamic Energy Regulation and Later-Life Phenotype of Male Wistar Rat Offspring

SCOPE

High-folic-acid diets during pregnancy result in obesity in the offspring, associated with altered DNA-methylation of hypothalamic food intake neurons. Like folic acid, the methyl-donor choline modulates foetal brain development, but its long-term programing effects on energy regulation remain undefined. This study aims to describe the effect of choline intake during pregnancy on offspring phenotype and hypothalamic energy-regulatory mechanisms.

METHODS AND RESULTS

Wistar rat dams are fed an AIN-93G diet with recommended choline (RC, 1 g kg^-1 diet), low choline (LC, 0.5-fold), or high choline (HC, 2.5-fold) during pregnancy. Male pups are terminated at birth and 17 weeks post-weaning. Brain 1-carbon metabolites, body weight, food intake, energy expenditure, plasma hormones, and protein expression of hypothalamic neuropeptides are measured. HC pups have higher expression of the orexigenic neuropeptide-Y neurons at birth, consistent with higher cumulative food intake and body weight gain post-weaning compared to RC and LC offspring. LC pups have lower leptin receptor expression at birth and lower energy expenditure and activity during adulthood.

CONCLUSION

Choline content of diets that are consumed by rats during pregnancy affects the later-life phenotype of offspring, associated with altered in utero programing of hypothalamic food intake regulation.

Effects of Moderate Chronic Food Restriction on the Development of Postprandial Dyslipidemia with Ageing

Ageing is a major risk factor for the development of metabolic disorders linked to dyslipidemia, usually accompanied by increased adiposity. The goal of this work was to investigate whether avoiding an excessive increase in adiposity with ageing, via moderate chronic food restriction (FR), ameliorates postprandial dyslipidemia in a rat model of metabolic syndrome associated with ageing. Accordingly, we performed an oral lipid loading test (OLLT) in mature middle-aged (7 months) and middle-old-aged (24 months) Wistar rats fed ad libitum (AL) or under moderate FR for 3 months. Briefly, overnight fasted rats were orally administered a bolus of extra-virgin olive oil (1 mL/Kg of body weight) and blood samples were taken from the tail vein before fat load (t = 0) and 30, 60, 90, 120, 180, and 240 min after fat administration. Changes in serum lipids, glucose, insulin, and glucagon levels were measured at different time-points. Expression of liver and adipose tissue metabolic genes were also determined before (t = 0) and after the fat load (t = 240 min). Postprandial dyslipidemia progressively increased with ageing and this could be associated with hepatic ChREBP activity. Interestingly, moderate chronic FR reduced adiposity and avoided excessive postprandial hypertriglyceridemia in 7- and 24-month-old Wistar rats, strengthening the association between postprandial triglyceride levels and adiposity. The 24-month-old rats needed more insulin to maintain postprandial normoglycemia; nevertheless, hyperglycemia occurred at 240 min after fat administration. FR did not alter the fasted serum glucose levels but it markedly decreased glucagon excursion during the OLLT and the postprandial rise of glycemia in the 24-month-old rats, and FGF21 in the 7-month-old Wistar rats. Hence, our results pointed to an important role of FR in postprandial energy metabolism and insulin resistance in ageing. Lastly, our data support the idea that the vWAT might function as an ectopic site for fat deposition in 7-month-old and in 24-month-old Wistar rats that could increase their browning capacity in response to an acute fat load.

Host genetics and diet composition interact to modulate gut microbiota and predisposition to metabolic syndrome in spontaneously hypertensive stroke-prone rats

Metabolic syndrome encompasses obesity, glucose intolerance, hypertension, and dyslipidemia; however, the interactions between diet and host physiology that predispose to metabolic syndrome are incompletely understood. Here, we explored the effects of a high-fat diet (HFD) on energy balance, gut microbiota, and risk factors of metabolic syndrome in spontaneously hypertensive stroke-prone (SHRSP) and Wistar-Kyoto (WKY) rats. We found that the SHRSP rats were hypertensive, hyperphagic, less sensitive to hypophagic effects of exendin-4, and expended more energy with diminished sensitivity to sympathetic blockade compared to WKY rats. Notably, key thermogenic markers in brown and retroperitoneal adipose tissues and skeletal muscle were up-regulated in SHRSP than WKY rats. Although HFD promoted weight gain, adiposity, glucose intolerance, hypertriglyceridemia, hepatic lipidosis, and hyperleptinemia in both SHRSP and WKY rats, the SHRSP rats weighed less but had comparable percent adiposity to WKY rats, which supports the use of HFD-fed SHRSP rats as a unique model for studying the metabolically obese normal weight (MONW) phenotype in humans. Despite distinct strain differences in gut microbiota composition, diet had a preponderant impact on gut flora with some of the taxa being strongly associated with key metabolic parameters. Together, we provide evidence that interactions between host genetics and diet modulate gut microbiota and predispose SHRSP rats to develop metabolic syndrome.-Singh, A., Zapata, R. C., Pezeshki, A., Workentine, M. L., Chelikani, P. K. Host genetics and diet composition interact to modulate gut microbiota and predisposition to metabolic syndrome in spontaneously hypertensive stroke-prone rats.

Grape pomace extract induced beige cells in white adipose tissue from rats and in 3T3-L1 adipocytes

This study investigated the effects of a grape pomace extract (GPE) rich in phenolic compounds on brown-like adipocyte induction and adiposity in spontaneously hypertensive (SHR) and control normotensive Wistar-Kyoto (WKY) rats fed a high-fat diet (HFD). HFD consumption for 10 weeks significantly increased epididymal white adipose tissue (eWAT) in WKY but not in SHR rats. Supplementation with GPE (300 mg/kg body weight/day) reduced adipocyte diameter and increased levels of proteins that participate in adipogenesis and angiogenesis, i.e., peroxisome-proliferator activated receptor gamma (PPARγ), vascular endothelial grow factor-A (VEGF-A) and its receptor 2 (VEGF-R2), and partially increased the uncoupling protein 1 (UCP-1) in WKY. In both strains, GPE attenuated adipose inflammation. In eWAT from SHR, GPE increased the expression of proteins involved in adipose tissue "browning," i.e., PPARγ-coactivator-1α (PGC-1α), PPARγ, PR domain containing 16 (PRDM16) and UCP-1. In primary cultures of SHR adipocytes, GPE-induced UCP-1 up-regulation was dependent on p38 and ERK activation. Accordingly, in 3T3-L1 adipocytes treated with palmitate, the addition of GPE (30 μM) activated the β-adrenergic signaling cascade (PKA, AMPK, p38, ERK). This led to the associated up-regulation of proteins involved in mitochondrial biogenesis (PGC-1α, PPARγ, PRDM16 and UCP-1) and fatty acid oxidation (ATGL). These effects were similar to those exerted by (-)-epicatechin and quercetin, major phenolic compounds in GPE. Overall, in HFD-fed rats, supplementation with GPE promoted brown-like cell formation in eWAT and diminished adipose dysfunction. Thus, winemaking residues, rich in bioactive compounds, could be useful to mitigate the adverse effects of HFD-induced adipose dysfunction.

Influencing Factors of Thermogenic Adipose Tissue Activity

Obesity is an escalating public health challenge and contributes tremendously to the disease burden globally. New therapeutic strategies are required to alleviate the health impact of obesity-related metabolic dysfunction. Brown adipose tissue (BAT) is specialized for dissipating chemical energy for thermogenesis as a defense against cold environment. Intriguingly, the brown-fat like adipocytes that dispersed throughout white adipose tissue (WAT) in rodents and humans, called "brite" or "beige" adipocytes, share similar thermogenic characteristics to brown adipocytes. Recently, researchers have focused on cognition of these thermogenic adipose tissues. Some factors have been identified to regulate the development and function of thermogenic adipose tissues. Cold exposure, pharmacological conditions, and lifestyle can enhance non-shivering thermogenesis and metabolism via some mechanisms. However, environmental pollutants, such as ambient fine particulates and ozone, may impair the function of these thermogenic adipose tissues and thereby induce metabolic dysfunction. In this review, the origin, function and influencing factors of thermogenic adipose tissues were summarized and it will provide insights into identifying new therapeutic strategies for the treatment of obesity and obesity-related diseases.

The intake of high-fat diets induces the acquisition of brown adipocyte gene expression features in white adipose tissue

BACKGROUND/OBJECTIVE

White-to-brown adipose tissue remodeling (browning) in response to different stimuli constitutes an active research area for obesity treatment. The emergence in traditional white adipose tissue (WAT) depots of multilocular adipocytes that express uncoupling protein 1 (UCP1) and resemble brown adipocytes, the so called 'brite' adipocytes, could contribute to increased energy expenditure. In rodents, obesogenic stimuli such as the intake of hyperlipidic diets can increase brown adipose tissue (BAT) thermogenic capacity and contribute to maintaining body weight. The aim of this study was to investigate the potential of two different hyperlipidic diets, a commercial high-fat (HF) diet and a highly palatable cafeteria (CAF) diet, to induce WAT browning.

METHODS

We analyzed gene expression of a wide number of brown/brite adipocyte markers in different WAT depots, in BAT and in peripheral blood mononuclear cells (PBMCs) increasingly being used in nutrition studies as a potential source of biomarkers of physiological effects. We also performed morphological analysis of adipose tissue.

RESULTS

Both HF diets studied were able to increase the expression of the markers studied in WAT in a depot-specific manner, as well as in BAT; some of these changes were also reflected in PBMCs. This increased browning capacity was translated into the appearance of UCP1- and CIDE-A (cell death-inducing DFFA-like effector A)-positive brite adipocytes in retroperitoneal WAT. Administration of the CAF diet, associated with higher adiposity, produced the strongest impact on the parameters studied while its withdrawal restored basal conditions.

CONCLUSIONS

Acquisition of brown adipocyte features in WAT could evidence an adaptation to try to counteract increased adiposity due to the intake of HF diets. Additionally, PBMCs could constitute an interesting easily obtainable material to assess the effect of nutritional interventions on browning capacity.

Rats of hypertensive ISIAH strain are resistant to the development of metabolic syndrome induced by high-fat diet

We studied the influence of high-fat diet on the development of metabolic syndrome in rats of hypertensive ISIAH strain and normotensive WAG strain. In contrast to ISIAH rats, high-fat diet in WAG rats led visceral obesity, glucose tolerance, and dyslipidemia. DNA-binding activity of the peroxisome proliferator-activated receptor α (PPARα) decreased in the liver of WAG rats and increased in ISIAH rats. Blood levels of TNF-α, IL-6, and corticosterone increased more significantly in WAG rats. Corticosterone content in the adrenal glands was more markedly reduced in WAG rats. High-fat diet had no effect on BP in ISIAH and WAG rats. It was concluded that ISIAH rats can be used as a genetic model in studies of the mechanism of resistance to the metabolic syndrome.

Expression of "brown-in-white" adipocyte biomarkers shows gender differences and the influence of early dietary exposure

Induction of brown-like adipocytes (brite) in white adipose tissues may allow the conversion of lipid storage cells in fat-burning cells. Little is known concerning browning potential in males compared with females. In this study, we aimed to analyse whether gender differences were present in gene expression of "brite" markers as well as the impact of dietary manipulation at both early stages and adulthood in rats. We have determined the expression of brite markers and genes associated with lipid and energy metabolism in inguinal adipose tissue in adult male and female rats. We have analysed the impact of high-fat (HF) diet in adult life and of early leucine supplementation (2 %) during lactation. Results show that although both genders have the potential to induce brite genes in inguinal adipose tissue, males expressed higher levels (CIDEA, HOXC9 and SHOX2), which would imply a higher browning capacity in comparison with females. Minor impact of HF diet in adult life was observed in most of the genes studied. Interestingly, results showed that early Leu was able to compromise the metabolic fate of white and brite adipocytes later in adult life. Leucine supplementation programmed higher expression of cell death-inducing DFFA-like effector, accompanied with induction of sterol regulatory element binding transcription 1c factor and lower UPC2 expression, particularly in females. In addition, Leucine supplementation was associated with higher expression of leptin and PPARγ and decreased carnitine palmitoyl transferase in both genders. Although the exact role of these adaptations needs further comprehensive analysis, dietary Leu supplementation at early age programmed inguinal adipose tissue in a gender specific manner.