**1. Introduction**

Diabetes mellitus (DM), often known as diabetes, is a metabolic syndrome caused by abnormalities in the body's capacity to generate insulin and/or activate insulin, or both. Hyperglycemia and glucose intolerance are the symptoms of diabetes mellitus [1]. Hyperglycemia increases the complications in the microvascular system (neuropathy, retinopathy, and nephropathy) as well as in the macrovascular system (stroke, ischemic heart disease, and peripheral vascular disease). As a result, there is a marked increase in morbidity and a significant decline in the quality of life [2–4]. According to the World Health Organization (WHO), 420 million people worldwide have diabetes, and the prevalence was estimated to be 2.8% in 2000, rising to 4.8% by 2030. Over the last two decades, the disease has been more prevalent than expected [5]. DM is seen as a huge global health and economic burden in the aging population and is now the eighth biggest cause of mortality globally [6]. The number of diabetics in India alone is already over 40 million, and by 2030, the country will have the biggest diabetic population in the world with a population of over 90 million [7, 8].

Diabetes has three basic subtypes: type 1, type 2, and gestational diabetes [9–11]. About 10% of all cases of diabetes are type 1 diabetes (T1DM), which is characterized by the impairment of insulin-secreting B-cells and needs daily insulin therapy for survival [12, 13]. T1DM is becoming more common in the world as a result of ineffective preventative and treatment approaches. Therefore, a thorough understanding of T1DM's pathophysiology is necessary. Environmental factors and genetic factors play a crucial role in the progression of T1DM [14, 15]. Most people with diabetes (90– 95%) have type 2 diabetes (T2DM), which is defined by impaired lipid and glucose metabolism brought on by insufficient insulin production or by its insensitivity [1]. Although T2DM is mostly diagnosed in older persons, the frequency of the condition in youngsters has been shown to rise as a result of obesity and physical inactivity [16]. Smoking, hereditary factors, excessive calorie consumption, and sedentary lifestyle are the main risk factors for T2DM, with alteration in gut microbiota as one of the causes and associated comorbidities [17]. A common problem that affects roughly 2–5% of all pregnancies, gestational diabetes mellitus (GDM) is characterized by high glucose levels in the second and third trimesters of pregnancy. It may manifest as either type I or type II diabetes in persons who have an inherited tendency to have the disease [18]. In the future, T2DM is more likely to occur in women with GDM due to their increased risk of pregnancy problems and premature birth [19, 20].

As per epidemiological observations, one of the characteristics of diabetic patients is changes in the diversity of intestinal microflora. Additionally, there is increasing evidence that diabetes and intestinal microflora are closely related. The microflora, host cells, and nutrients make a complex ecosystem that creates up the human gut. The alimentary canal contains about 100 trillion bacteria, which together make up the intestinal flora [21]. The bacteria that make up the intestinal flora are numerous and diverse. Genus, family, order, and phylum classifications are used to taxonomically group these. In healthy adults, the six phyla *Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, Fusobacteria*, and *Verrucomicrobia* make up most of the intestinal microflora [22]. Researchers have shown that gut microbiota in diabetics is less reliable than in healthy individuals. In a sick condition functionality of gut microbiota changes, a human metagenome-wide association study conducted in Europe and China found surprising connections between specific bacterial genes, gut microbes, and the digestive system in T2DM patients [23]. These individuals showed greater levels of *Lactobacillus* spp. than nondiabetics, and fasting glucose and glycated hemoglobin (HbA1c) levels are positively connected with these levels [24]. *Clostridium* spp. had a negative relationship with fasting blood sugar and plasma triglycerides [25]. According to one investigation, it has been found that the number of *Prevotella* and *Faecalibacterium* decreased in diabetic conditions and demonstrated that the microbiome impacts both T1DM and T2DM [26]. In the mucous layer, there is an increase in *Akkermansia muciniphila* after metformin therapy [27]. It has been hypothesized that type 1 diabetes (T1DM) and autoimmune diabetes may both develop due to inflammation [28]. Autoimmune diabetes has been related to the microbiota of the gut because of the common receptors in the inflamed pancreas and the gut [29].

Diabetes interventions include medication [30], nutritional care [31, 32], physical activity [32], or weight control [33, 34]. They might also involve education, coaching, or social support [35]. As stated above, diabetes affects the gut microbiome; therefore, probiotics can be employed as one of the nutritional interventions. These are live bacteria that are given in sufficient amounts and continue to remain in the gut bionetwork to have a beneficial impact on one's health [36]. Lilly and Stillwell used the word "probiotics" to refer to "organisms and substances which contribute

### *Probiotics in the Management of Diabetes DOI: http://dx.doi.org/10.5772/intechopen.110338*

to intestinal microbial balance" [37]. Probiotics are "organisms and compounds that help to gut microbial equilibrium," according to Parker [38]. The International Scientific Association for Probiotics and Prebiotics (ISAPP), which was supported by the Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO, 2001), defined probiotics as "Live microorganisms which, when administered in adequate amounts, confer a health benefit on the host" [39]. Probiotics are defined by the World Health Organization (WHO) as "products or preparations containing live, designated microorganisms in appropriate quantities that give positive effects on the host by altering its gut microbiota" [40].

Probiotics play an important role in immune system development, immune system homeostasis, and epithelial cell differentiation and proliferation [41]. Probiotics are not a recent discovery but have been present in many of our traditional foods for a long time, including drinks, salty fish, yogurt, various types of cheese, and so forth. Before the invention of the microscope, people were able to prepare a variety of milk products with various flavors and structures [42]. This is the result of various microbial reactions brought on by various microbes [43]. We really had no idea how probiotic-containing foods were first used, especially for therapeutic purposes. It is possible that Ilya Ilyich Metchnikoff, who won the Nobel Prize in Medicine in 1908, was the first to notice the effects of what is now known as probiotics while working at the Pasteur Institute. He correlated the consumption of yogurt's microorganisms with good health. He proposed in 1907 that the bacteria *Lactobacillus bulgaricus* and *Streptococcus thermophilus*, which are involved in yogurt fermentation, block the putrefactive-type fermentations of the intestinal flora. He linked the consumption of yogurt containing the *Lactobacillus* species to the longevity and good health of Bulgarian peasants, and he presented his findings to the public in a manner that was easily understood [44].

The ISAPP consensus panel explained the concept that some probiotic mechanisms may be expressed by most strains of a larger taxonomic group, which is an evolving idea regarding the strain specificity of probiotic effects [45]. Lactic acid bacteria (LAB) are a group of predominant gut-friendly bacteria found in the digestive tract [46] and suppress pathogens through their secretions [47]. For instance, the majority of *Bifidobacterium* and *Lactobacillus* species both produce organic acids like lactate and acetate. There are several potential advantages for the gastrointestinal system. The inhibition of harmful microbes and the cross-feeding of other advantageous gut microbes result in the production of butyrate, which plays a significant role in cultivating a healthier gut environment [48]. The types of microbes from the genera *Lactobacillus, Bifidobacterium*, and *Saccharomyces* that are most frequently used as probiotics include these. Other genera of probiotics include *Escherichia, Propionibacterium, Streptococcus*, and *Bacillus*. Probiotics are poised to be an important tool for influencing the gut ecosystem's function to enhance the nutritional status and health [49, 50]. The mechanisms of action that researchers have identified in various probiotic strains against diabetes are shown in **Figure 1**. However, there are still a lot of gaps in our understanding of the mechanisms underlying health benefits.

Modification of the gut microbiota's composition is one alleged probiotic effect that has been challenging to prove in healthy humans. Although it is widely believed that probiotics "support a healthy intestinal flora," [51], probiotic organisms seldom survive for longer than a few weeks after consumption [52]. Alpha diversity, richness, and evenness of the fecal microbiota were examined in a systematic review of studies looking at the effects of probiotics [51].

**Figure 1.** *Potential mechanisms linking probiotics to diabetes.*

Research is still finding links between the microbiota and diabetes, and these seem to involve a variety of metabolic and immune response processes, most of which are linked to more specific mechanisms. Future investigations into the relationship between variations in the gut microbiota balance and diabetes may result in new interventional studies. This review provides an overview of the role of probiotics in diabetes management.
