Nutrient-adjusted high-fat diet is associated with absence of periepididymal adipose tissue inflammation: is there a link with adequate micronutrient levels?

The aim of this study was to investigate the real impact of dietary lipids on metabolic and inflammatory response in rat white adipose tissue. Male healthy Wistar rats were fed ad libitum with a control diet (CON, n=12) or with an adjusted high-fat diet (HFD, n=12) for 12 weeks. Oral glucose and insulin tolerance tests were performed during the last week of the protocol. Plasma fatty acid, lipid profile, body adiposity, and carcass chemical composition were analyzed. Plasma concentration of leptin, adiponectin, C-reactive protein (CRP), TNF-α, IL-6, and monocyte chemotactic protein (MCP-1) was measured. Periepididymal adipose tissue was employed to evaluate TNF-α, MCP-1, and adiponectin gene expression as well as NF-κB pathway and AKT proteins. Isocaloric intake of the adjusted HFD did not induce hyperphagia, but promoted an increase in periepididymal (HFD = 2.94 ± 0.77 vs. CON = 1.99 ± 0.26 g/100 g body weight, p = 0.01) and retroperitoneal adiposity (HFD = 3.11 ± 0.81 vs. CON = 2.08 ± 0.39 g/100 g body weight, p = 0.01) and total body lipid content (HFD = 105.3 ± 20.8 vs. CON = 80.5 ± 7.6 g carcass, p = 0.03). Compared with control rats, HFD rats developed glucose intolerance (p=0.01), dyslipidemia (p = 0.02) and exhibited higher C-reactive protein levels in response to the HFD (HFD = 1002 ± 168 vs. CON = 611 ± 260 ng/mL, p = 0.01). The adjusted HFD did not affect adipokine gene expression or proteins involved in inflammatory signaling, but decreased AKT phosphorylation after insulin stimulation in periepididymal adipose tissue (p = 0.01). In this study, nutrient-adjusted HFD did not induce periepididymal adipose tissue inflammation in rats, suggesting that the composition of HFD differently modulates inflammation in rats, and adequate micronutrient levels may also influence inflammatory pathways.