There’s nothing sweet about out-of-control blood sugars. Yet billions across the globe struggle to steady the high numbers broadly labelled as diabetes.

Diabetes, the Problem

A look at the three types of diabetes:

• Type 1 diabetes: Beta cell destruction in the pancreas, possibly enabled when dysbiosis fails to prevent antigen attacks on beta cells
• Gestational diabetes: caused by stresses of pregnancy
• Type 2 diabetes: Impaired insulin production and insulin resistance

Role for Microbes

While different roads lead to the various forms of diabetes, microbes appear to be backseat drivers for all of them though most evidence thus far addresses the last, Type 2 diabetes, which can come on gradually through insulin resistance.

Dysbiosis — imbalance of the gut microbial ecosystem — often exists in insulin resistance. Emerging evidence in rodents and humans suggests that dysbiosis leads to the following sequence of unhealthy events: Increased gut permeability which in turn allows leakage of endotoxins into the blood which causes systemic low-grade inflammation. And reversing it, a healthy microbiota may restore normal conditions. One recent study from the Netherlands found that transfer of intestinal microbiota from lean donors to individuals with metabolic syndrome increased insulin sensitivity as well as butyrate-producing microbes which are linked to better control.

Other Evidence that Microbes are Involved in Blood Sugar Control:

• Studies indicate that Type 2 diabetics have fewer Firmicutes and more Bacteroidetes and Proteobacteria than controls.
• Insulin resistance and dysbiosis can be induced quickly in rats that have been overfed high-fat foods.
• One recent study revealed that probiotic supplementation preserved glycemic control in humans during a high-fat diet period.

Can Probiotics Help?

The data on the use of probiotics to improve glycemic control is inconsistent yet provocative the same.

• A 2015 meta-analysis of randomized controlled trials concluded that probiotics may have a modest effect on glycemic control, but that even these small changes can be beneficial.
• Another meta-analysis done around the same period recorded significant drops in HbA1c (a biomarker which rises as blood sugar control worsens) but there were no differences in fasting blood glucose or insulin concentrations for those consuming probiotics.
• And just this year, an analysis of several other data sets looked at results of probiotic supplementation on patients with Type 2 diabetes. They found significant drops in fasting blood glucose and insulin concentrations but no change in HbA1c. Therefore conflicting data abounds.

Hence type and amounts of probiotics in addition to the duration of studies are confounders as well as individual subject uniqueness.

Mechanism of Action

Low-grade inflammation, and in particular endotoxemia such as high amounts of gut microbiota-derived lipopolysaccharide LPS in plasma, is involved in the onset and progression of insulin resistance in both rodent and human models, according to a recent review in The British Journal of Nutrition. A high fat content in the diet and changes in barrier function are purported factors in endotoxemia.

In that review, Peter Bron and colleagues also reported that several studies show both diet-induced and genetic type 2 diabetic mice displayed changes in gut microbiota. Bifidobacteria is reduced and this has been linked to reduced intestinal LPS levels and improved mucosal barrier function in mice.

Prebiotics restore bifidobacterial colonies in the intestines which leads to the reduction of metabolic endotoxemia, gut barrier dysfunction and inflammation. Only a few human studies have been conducted testing the benefit but are promising.

In addition to prebiotic influence, probiotic supplementation may have beneficial effects in Type 2 diabetes. Various lactobacilli were shown to positively affect various metabolic disorder parameters. For example, a strain of Lactobacillus casei "induced a reduction of insulin resistance separate from any change in fat mass and body weight." Akkermansia muciniphila "also has been shown to reinforce gut barrier function leading to" reduced inflammation and metabolic endotoxemia upon high-fat-diet feeding in diabetic mice.

Fortifying intestinal mucosal walls and producing butyrate are two mechanisms of actions according to a recent review in Diabetes and Metabolism Journal.

Final Remarks

In conclusion, prebiotics and probiotics are known to reduce the core problems inherent in guts of diabetics: excess gut permeability, endotoxemia and inflammatory response. Probiotics may be added with fermented food products or supplements. Feeding the microbes with prebiotics such as fructo-oligosaccharides is imperative to achieve flourishing colonies of good bacteria.