Brown Seaweed Sargassum siliquosum as an Intervention for Diet-Induced Obesity in Male Wistar Rats

Abstract

The therapeutic potential of Sargassum siliquosum grown in Australian tropical waters was tested in a rat model of metabolic syndrome. Forty-eight male Wistar rats were divided into four groups of 12 rats and each group was fed a different diet for 16 weeks: corn starch diet (C); high-carbohydrate, high-fat diet (H) containing fructose, sucrose, saturated and trans fats; and C or H diets with 5% S. siliquosum mixed into the food from weeks 9 to 16 (CS and HS). Obesity, hypertension, dyslipidaemia, impaired glucose tolerance, fatty liver and left ventricular fibrosis developed in H rats. In HS rats, S. siliquosum decreased body weight (H, 547 ± 14; HS, 490 ± 16 g), fat mass (H, 248 ± 27; HS, 193 ± 19 g), abdominal fat deposition and liver fat vacuole size but did not reverse cardiovascular and liver effects. H rats showed marked changes in gut microbiota compared to C rats, while S. siliquosum supplementation increased gut microbiota belonging to the family Muribaculaceae. This selective increase in gut microbiota likely complements the prebiotic actions of the alginates. Thus, S. siliquosum may be a useful dietary additive to decrease abdominal and liver fat deposition.

Nannochloropsis oceanica as a Microalgal Food Intervention in Diet-Induced Metabolic Syndrome in Rats

“…The diet-induced changes in metabolic, cardiovascular and liver parameters in the rat model used in this project mimic the changes in human metabolic syndrome [16]. Interventions with seaweeds have been previously shown to reverse these changes [19][20][21]. This study shows that high-carbohydrate, high-fat diet-fed rats supplemented with the microalgae N. oceanica had higher lean mass and lower abdominal and liver fat than rats fed only the obesogenic diet.…”

“…The diet-induced changes in metabolic, cardiovascular and liver parameters in the rat model used in this project mimic the changes in human metabolic syndrome [16]. Interventions with seaweeds have been previously shown to reverse these changes [19][20][21]. The relative abundance of bacteria from the class Bacteroidia and Erysipelotrichia was increased in C and CN rats (Bacteroidia: C, 29.00%; CN, 29.63%; p > 0.05; Erysipelotrichia: C, 9.31%; CN, 8.21%; p < 0.01) compared to H and HN rats (Bacteroidia: H, 17.17%; HN, 12.12%; p > 0.05; Erysipelotrichia: H, 4.35%; HN, 3.93%; p < 0.01).…”

“…The search for microbial signatures of disease has led to the use of changes in the Firmicutes/Bacteroidetes ratio as a marker of obesity; however, use of this ratio may not be valid to determine health status because of lifestyle-associated variations in patients from a single population [36]. Our previous studies have shown interaction of polysaccharides from macroalgal interventions with the gut microbiota in improving metabolic and cardiovascular health [19][20][21]. As an example, our study on the macroalgae Caulerpa lentillifera showed correlations between gut microbiota and 15 physiological variables, especially oral glucose tolerance, liver weight and abdominal fat pads [21].…”

“…Batches of 5 L were freeze-dried for 36-48 h at 0.011 mbar and −60 • C. The powder was stored at 4 • C in sealed plastic containers until feeding or analysis. The composition of N. oceanica was obtained as described previously [19].…”

Research Progresses on the Physiological and Pharmacological Benefits of Microalgae-Derived Biomolecules

“…The animals were fed a diet with or without supplementation of 10% Nannochloropsis gaditana for 2 months. The results showed that the Nannochloropsis gaditana supplementation reduced their blood glucose and HbA1c levels and attenuated the amount of tissue oxidative stress and inflammation, which resulted in the improvements of functions in the liver and kidney of the diabetic rats [ 80 ].…”