Lean and obese microbiota: differences in in vitro fermentation of food-by-products

Characterization of a novel type 4 resistant starch from tapioca and its obesity-preventive effects through gut microbiota modulation in high-fat diet-treated mice

The rising pandemic of obesity has received significant attention. Yet, more safe and effective targeted strategies must be used to mitigate its impact on individual health and the global disease burden. While the health benefits of resistant starch (RS) are well-documented, the role of RT-90 (a phosphate-modified tapioca RS containing 90.1 % total dietary fiber) in mitigating obesity remains unknown. Accordingly, the physicochemical characteristics and protective effects of RT-90 on obesity were investigated in high-fat diet (HFD)-fed mice. Physicochemical property examinations showed that RT-90 consisted of small, round starch granules (D90: 20.69 ± 0.4 μm) with a crystalline structure, P-O-C stretching, and high peak melting temperature and enthalpy. Additionally, feeding mice with RT-90 significantly decreased body weight, improved oral glucose tolerance test (OGTT), reduced fatty liver and adipose tissue accumulation, lowered oxidative stress and inflammation by upregulating antioxidant enzymes (SOD, catalase, GPx) and anti-inflammatory cytokines (IL-4, IL-10), and enhanced fecal lipids and bile acid excretion. Notably, RT-90 administration in HFD-fed mice was associated with the inhibition of obesity-associated harmful bacteria ([Eubacterium]_xylanophilum group, Allobaculum, Clostridia_UCG-014, Dubosiella) and promotion of short-chain fatty acids (SCFAs)-producing gut flora, including Bifidobacterium, Lactobacillus, Bacteroides, and Parabacteroides, which suggests a possible mechanism by which RT-90 alters gut microbiota to attenuate obesity. These novel findings first revealed that RT-90 facilitates weight loss through its antioxidant, anti-inflammatory, and microbiota modulation abilities. This provides a promising strategy for managing overweight or obesity and holds potential for applications in developing healthy food products.

In vitro models as a tool to study the role of gut microbiota in obesity

Obesity, a highly prevalent condition worldwide that leads to the development of multiple metabolic diseases, has been related to gut microbial dysbiosis. To understand this correlation, in vivo models have been extremely useful. However, its use is limited by associated ethical concerns, high costs, low representativeness, and low reproducibility. Therefore, new and improved in vitro models have been developed in recent years, representing a promising tool in the study of the role of gut microbiota modulation in weight management and metabolic health. This review aims to provide an update on the main findings obtained in vitro regarding gut microbiota modulation with probiotics, and food compounds, and its interaction with the host metabolism, associated with obesity. Available in vitro colon models currently used to study obesity are discussed, including batch and dynamic fermentation systems, and models that allow the study of microbiota-host interactions using cell cultures. In vitro models have demonstrated that homeostatic microbiota may help overcome obesity by producing satiety-related neurotransmitters and metabolites that protect the gut barrier and improve the metabolic activity of adipose tissue. In vitro models may be the key to finding new treatments for obesity-related disorders.