Macadamia oil supplementation attenuates inflammation and adipocyte hypertrophy in obese mice

Abstract

Excess of saturated fatty acids in the diet has been associated with obesity, leading to systemic disruption of insulin signaling, glucose intolerance, and inflammation. Macadamia oil administration has been shown to improve lipid profile in humans. We evaluated the effect of macadamia oil supplementation on insulin sensitivity, inflammation, lipid profile, and adipocyte size in high-fat diet (HF) induced obesity in mice. C57BL/6 male mice (8 weeks) were divided into four groups: (a) control diet (CD), (b) HF, (c) CD supplemented with macadamia oil by gavage at 2 g/Kg of body weight, three times per week, for 12 weeks (CD + MO), and (d) HF diet supplemented with macadamia oil (HF + MO). CD and HF mice were supplemented with water. HF mice showed hypercholesterolemia and decreased insulin sensitivity as also previously shown. HF induced inflammation in adipose tissue and peritoneal macrophages, as well as adipocyte hypertrophy. Macadamia oil supplementation attenuated hypertrophy of adipocytes and inflammation in the adipose tissue and macrophages.

Figures

Figure 1

Effect of MO supplementation on adipose tissue histology. (a) Histological sections stained with H&E. (b) Area of adipocytes. CD = group of animals maintained on control diet; HF = group of animals fed high-fat diet; CD + MO = group of animals fed control diet supplemented with macadamia oil; HF + MO = group of animals fed high-fat diet supplemented with macadamia oil. The data are given as the means ± S.D. *P < 0.05 (n = 6).

Figure 2

Insulin sensitivity and triacylglycerol content in skeletal muscle after 12 weeks. (a) HOMA-IR: homeostatic model assessment of insulin resistance; (b) GLUT-4 gene expression; (c) triacylglycerol content in gastrocnemius muscle. The data are given as the means ± S.D. In all experiments the animals were previously fasted for 6 hours. CD = group of animals maintained on control diet; HF = group of animals fed high-fat diet; CD + MO = group of animals fed control diet supplemented with macadamia oil; HF + MO = group of animals fed high-fat diet supplemented with macadamia oil. A.U. = arbitrary unit. *P < 0.05; **P < 0.01 (n = 6).

Figure 3

Inflammatory parameters in adipose tissue homogenate and adipose tissue explant incubation medium. IL10 content in adipose tissue homogenate (a) and IL1-β in the adipose tissue explant incubation medium, after 24 hours measured by ELISA (b). The animals received water or macadamia oil orally, 2 g/kg b.w., with or without association with a high-fat diet. CD = group of animals maintained on control diet; HF = group of animals fed high-fat diet; CD + MO = group of animals fed control diet supplemented with macadamia oil; HF + MO = group of animals fed high-fat diet supplemented with macadamia oil. The data are given as the means ± S.D. *P < 0.05 (n = 5-6).

Figure 4

Nitric oxide and cytokine production by peritoneal macrophages. Peritoneal macrophages were collected and cultured for 24 h in the absence (white bars) or presence (black bars) of 2.5 μg/mL LPS. Nitric oxide (a), IL1-β (b), TNF-α (c), IL-6 (d), and IL-10 (e) were measured. CD = control diet; HF = high-fat diet; CD + MO = control diet + macadamia oil; HF + MO = high-fat diet + macadamia oil. The data are given as the means ± S.D. *P < 0.05; ***P < 0.001 (n = 5-6).