Abstract
Aged black garlic (ABG) is a functional food with antioxidant and anti-inflammatory properties. Recent studies also report its beneficial metabolic effects in a context of obesity or diabetes, although the mechanisms involved are poorly understood. The aim of this work was to analyze the effects of an ABG extract in the vascular and metabolic alterations induced by a high-fat/sucrose diet in rats. For this purpose, male Sprague–Dawley rats were fed either a standard chow (controls; n = 12) or a high-fat/sucrose diet (HFD; n = 24) for 16 weeks. From week 8 on, half of the HFD rats were treated with a commercial ABG extract concentrated in S-allyl cysteine and melanoidins (ABG10+®; 250 mg/kg daily by gavage; 5 mL/kg). ABG10+®-treated rats showed lower mean caloric intake, body weight, triglycerides, low density lipoprotein cholesterol (LDL-c), insulin and leptin serum concentrations and higher high density lipoprotein cholesterol (HDL-c) and adiponectin serum concentrations than non-treated rats. In the hypothalamus, ABG10+® treatment induced an increase in the gene expression of proopiomelanocortin (POMC) and a decrease in leptin receptor (ObR) mRNA levels. No significant changes were found in visceral adipose tissue except for an overexpression of β3-adrenergic receptor (β3-ADR) in ABG-treated rats. In subcutaneous adipose tissue, ABG10+® treatment decreased adipose weight and downregulated the gene expression of PPAR-γ, LPL, ObR and HSL. In brown adipose tissue, an overexpression of InsR, GLUT-4, UCP-1 and β3-ADR in ABG10+®-treated rats was found, whereas PPAR-γ mRNA levels were significantly decreased. Regarding vascular function, ABG10+® treatment attenuated the obesity-induced vasoconstriction in response to potassium chloride both in presence/absence of perivascular adipose tissue (PVAT). On the contrary, aorta segments from ABG-treated rats showed and improved relaxation in response to acetylcholine only when PVAT was present, with this fact possible being related to the decreased gene expression of proinflammatory cytokines in this tissue. In conclusion, ABG10+® administration partially improves the metabolic and vascular alterations induced by a high-fat/high-sucrose diet in rats through modifications in the gene expression of proteins and neuropeptides involved in inflammation, fat metabolism and food intake regulation. Further studies are required to assess the bioavailability of ABG between rats and humans.
Highlights
In recent decades, increased life expectancy, sedentary lifestyle and consumption of foods rich in saturated fats and added sugars have exposed the population of the developed countries to emerging health problems
Adipose tissue depots are subjected to extensive hypertrophy and to the secretion of adipokines and proinflammatory cytokines by both adipocytes and infiltrating immune cells [1], which derives in a condition of low-grade inflammation and in the development of insulin resistance in the long term [2]
The maximum absorbance at 280 nm was explained by the presence of phenolic compounds and aminoacids which are involved in the early Maillard reaction during ageing process, obtaining initial intermediates arising from sugar-amine condensation and Amadori rearrangement
Summary
In recent decades, increased life expectancy, sedentary lifestyle and consumption of foods rich in saturated fats and added sugars have exposed the population of the developed countries to emerging health problems. The steadily increasing incidence of obesity and associated morbidities is recognized as a major public health problem, reaching epidemics proportions in both industrialized and developing countries. In the past few years, numerous drugs have been approved for the treatment of obesity and its related co-morbidities. Most of them have been withdrawn from the market because of their adverse effects [3]. For this reason, finding a new drug with no side effects is the ultimate goal for many pharmaceutical companies
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