Metabolic disease (or metabolic syndrome) is the term given to a group of risk factors that increase risk of heart disease, stroke and diabetes.
Such factors include abdominal adiposity, dyslipidaemia, hypertension and hyperglycaemia. These metabolic risk factors are increasingly linked to dysbiosis of the intestinal microbiota.
High fat, high sugar diets have increasingly been shown to alter microbiota compositions substantially in animals, and several researchers have now shown that the transplant of obesogenic dysbiotic microbes into germ-free mice results in an increase in fat mass (Turnbaugh et al. 2006, Turnbaugh et al. 2009).
Such metabolic diseases and risk factors result in the activation of pro-inflammatory mechanisms and metabolic endotoxemia, which exacerbates the problem through promoting insulin resistance and other metabolic abnormalities. As probiotics have been described to reduce inflammation and intestinal permeability, and therefore have the potential to decrease metabolic endotoxemia, the application of probiotics as biotherapeutics are therefore considered as valuable alternatives to medical therapeutic approaches.
Although use of probiotics remains an emerging area of research, there have been some interesting findings to report. Early research with extracts of L. casei Shirota suggested a benefit in reducing hypertension (Nakajima et al. 1995, Watanuki et al. 1999) and provided a potential mechanism (Gonzalez-Gonzalez et al. 2011). A recent observational study concluded that the risk of developing hypertension is substantially lower in those who consume L. casei Shirota at least 3 times a week (Aoyagi et al. 2016). Metabolic effects of L. casei Shirota have also been studied in obese children (Nagata et al. 2017), obese pre-diabetic men (Naito et al. 2018) and patients with type 2 diabetes (Sato et al. 2017). Furthermore, a pilot study conducted in the UK has shown beneficial effects on blood glucose and insulin resistance in a healthy student population, as detailed here.
Study: Metabolic disease
Maintenance of blood glucose and insulin sensitivity - Hulston et al. (2015) Br J Nutr 113: 596-602.
Method: This randomised, open-label, controlled study conducted at Loughborough University in the UK, investigated whether L. casei Shirota can prevent insulin resistance induced by a short-term overfeeding. Seventeen healthy, normal weight and physically active participants were randomly assigned to a group receiving L. casei Shirota (1.3 x 1010 CFU/day x 4 weeks) or to a control group with no supplementation. Both groups ate their usual diet for 3 weeks and were challenged with a high-fat (65% of energy), high-energy (50% increase in energy intake) diet for one week. An oral glucose tolerance test (OGTT) was performed before and after the overfeeding. Blood glucose and insulin were also measured at the same timepoints.
Results: The high-fat, high-energy diet led to an increase in weight (P<0.05), fasting plasma glucose (P<0.05) and glucose area under the curve (AUG) in the OGTT by 10% (P<0.05), and a 27% decrease in insulin sensitivity (P < 0.05) in the control group. Whereas the increase in weight was not significant, and fasting plasma glucose, glucose AUC and insulin sensitivity did not change in the L. casei Shirota group.
Conclusion: The consumption of L. casei Shirota before and during a high-fat, high-energy diet may be useful in preventing insulin resistance and may play a role in the prevention of diet-induced metabolic diseases. This study is being followed up by a larger cohort to confirm the findings.