Psoriasis is a chronic disease alternating between flares and periods of remission, of variable length and intensity.

Epidermis renewing itself too quickly

In the vast majority of cases, psoriasis presents in the form of red patches covered with white scales, located primarily on the elbows, knees, scalp, and lower back. Although it is neither serious nor contagious, this cutaneous condition is, nevertheless, burdensome and has a serious impact on quality of life.

An impoverished intestinal microbiota

The mechanism for the inflammation that characterizes psoriasis is now known: the epidermis is replaced in 4 to 6 days instead of the normal 3 weeks, leading to an accumulation of dead skin and local inflammation. Conversely, the cause remains unknown. Several genetic and environmental risk factors have been identified, but now we need to understand how they interact. We know that stress, certain medications (beta blockers, anti-hypertensives, interferon alpha, etc.) and certain ENT infections increase the likelihood of flares. The role of the intestinal and cutaneous microbiota has also been highlighted. Indeed, an imbalance has been observed in the composition of the cutaneous microbiota in the psoriatic lesions compared to healthy skin, although the disease is not related to any pathogen in particular. For its part, it seems that the intestinal microbiota controls cutaneous inflammation by altering the immune response. The exact molecular mechanisms remain largely unknown. However, it is suspected that overrepresented pro-inflammatory bacteria cause the inflammation.

No cure

At present, no treatment exists to cure psoriasis.
Treatment is based on the application of corticosteroid-based products and vitamin D3 analogues during flares, combined with hydrating creams. Phototherapy is indicated in extended forms, but its use should be limited. Serious forms benefit from other treatments that should be carefully monitored. Research is currently being carried out to evaluate the impact of probiotics on localized cutaneous inflammation and dysbiosis.

Although they affect the face in 95% of cases, acne lesions can be observed on the back, neck, and the front of the thorax. A quarter of adults are affected, particularly women.

Diverse lesions

Acne is a disease of the hair follicles, combining the hair with a sebum-producing gland. This cutaneous condition is characterized by various kinds of lesions, depending on the stage: blackheads and whiteheads are the first stage of acne, then papules and pustules correspond to the inflammatory stage.

The role of the cutaneous microbiota

Genetics, hormones, hygiene…. There are many causes of acne but they all have one thing in common: the involvement of the bacteria Propionibacterium acnes in its development. This germ, naturally present on the skin, multiplies under the effect of excess sebum and leads to an imbalance in the cutaneous microbiota. The skin reacts to this local dysbiosis, creating inflammation.
It is now well-known that chronic skin diseases are often associated with other problems. This is the case for acne, where there is a serious prevalence of stress, anxiety, and depression associated with functional gastrointestinal disorders in people affected. The current hypothesis singles out altered interactions in the “gut-brain-skin” axis, which may cause local and systemic dysbioses and inflammation.

A tailor-made treatment

Acne treatment depends on its severity and its psychological impact. Topical and/or oral treatments (antibiotics or isotretinoin) associated with good hygiene generally give good results. However, with the emergence of antibiotic resistance, the search for a safe and effective alternative has become necessary. For several years, probiotics (local or oral) have been studied for therapeutic purposes. Some have notably shown the benefits of lactobacilli (Lactobacillus acidophilus and Lactobacillus paracasei) on the cutaneous barrier, skin sensitivity, hydration, and the functions of the epidermis.

The number of people affected by lupus is hard to determine. Its worldwide prevalence is estimated to vary between 10 and 150 cases for every 100,000 inhabitants, of whom the majority are women (85%).

When the immune system attacks its own cells

For reasons that remain unknown, the immune system in people afflicted with lupus produces autoantibodies, which cause inflammatory reactions and lesions that can affect all tissues. A whole range of symptoms results from lupus: fatigue, cutaneous eruptions, joint pain, dry eyes, hair loss, thrombosis, fever, pleurisy, and pericarditis. The disease progresses in flares of variable duration and intensity, which alternate with phases of remission. A diagnosis of lupus is confirmed by blood test, and the extent of the damage is measured with imaging examinations.

Predisposing factors but an unknown cause

Although the causes of lupusremain a mystery, several predisposing factors have been identified: estrogen, a genetic disposition, certain medications, UV rays, stress, and certain viruses (Epstein-Barr virus). Research work has also examined the role of the intestinal microbiota. Indeed, an imbalance (dysbiosis) was observed in lupus patients during the remission phase. The microbiota may even be involved in the production of autoantibodies.

Reduce and space out flares

No medication cures lupus. However, combining several molecules (nonsteroidal anti-inflammatories, antimalarials, corticosteroids, immunosuppressants, and monoclonal antibodies, depending on the severity of the disease) eases flares, limits complications, and lengthens the periods of remission. At the same time, less harsh long-term treatments prevent relapses.

If the role of the microbiota is confirmed, modulating it via diet or probiotics could become a promising therapeutic option.

Around 1% of the adult population suffers from rheumatoid arthritis (RA), with women affected more frequently than men.

An autoimmune disease that progresses in flares

RA is an autoimmune disease that develops in flares that cause persistent inflammation in the joints, primarily in the feet and hands. Swelling, pain, and stiffness of the joints are the primary symptoms. Without medical treatment, RA spreads to new joints and progressively deforms or even destroys them.

A genetic predisposition paired with microbiota imbalance

Although there are genes for RA predisposition, they are not enough to cause the disease. They interact with environmental factors, among which the intestinal and buccal microbiota are increasingly being considered. Indeed, patients present microbial imbalances (dysbioses) very similar to those observed in patients affected by inflammatory bowel diseases and which diminish with treatment.

Probiotics as adjuvant therapy

No current treatment cures RA, but there are means of slowing its progression and relieving symptoms: pain medications, control therapy (immunosuppressors or biopharmaceuticals), rehabilitation (physical therapy, ergotherapy, balneotherapy, etc.). Probiotics have recently been used as supplemental therapy, which is considered a promising approach.

Diet, sedentism, and microbiota to blame

In 2012, coronary artery disease caused 7.4 million deaths according to the WHO. It is most often a complication of atherosclerosis. It is the progressive depositing of fats on the walls of the coronary arteries--the arteries that supply blood to the heart muscle. These deposits gradually form an atheromatous plaque, which narrows the diameter of the arteries and reduces blood flow. Atherosclerosis is a result of various factors, including unbalanced diet and a lack of physical activity.

The severity of coronary artery disease depends on the extent of the area deprived of oxygen and the degree of arterial narrowing. There is, therefore, a distinction between angina, myocardial infarction, and sudden death.

Heart and microbiota: a connection?

Coronary artery disease may also be linked to the nature of the microbiota. Certain intestinal bacteria produce TMA (trimethylamine), a substance which, when oxidized in the liver, favors the formation of clots capable of clogging the smallest arteries, such as the coronary arteries that supply the heart.

Revascularizing the heart muscle

In the acute phase (myocardial infarction), the goal of treatment is to unblock the affected artery in order to supply oxygen to the heart muscle. In terms of prevention, the involvement of the intestinal microbiota in the development of coronary artery disease means several therapeutic applications can be envisaged: enrichment of the intestinal flora with non-TMA-producing bacteria via probiotics, the elimination of TMA-producing bacteria, or more radically, the transplantation of a low-TMA-producing fecal microbiota.

Atheromatous plaques, or lipid plaques consisting of cholesterol in particular, are very common; all adults have them. Their thickening can obstruct blood flow, meaning organs are no longer sufficiently supplied, which can lead to pain and changes in heart rate. A local inflammatory reaction can lead to plaque rupture. When plaques become unstable and break off, the results are dramatic: this is the cause of 80% of cases of sudden death. Plaque rupture can also cause myocardial infarction or stroke. Although there seems to be a genetic predisposition, risk factors have been identified: an excess of cholesterol and smoking.

Bacteria and diet in question

Intestinal microbiota may contribute to plaque vulnerability, and therefore to rupture. Some bacteria, as well as the components that they produce, could cause an inflammatory reaction that could eventually lead to atheromatous plaque rupture. Dysbiosis, an imbalance in the composition of the microbiota, might also increase the risk of atherosclerosis in cases of high lipid diets. Bacteria appear to play an important role, because it has even been shown that infections are risk factors for atherosclerosis--gum infections (periodontitis) in particular.

From prevention to probiotics

Prevention is crucial: diet, weight loss, stopping smoking, etc. However, some medications can have a beneficial effect in high-risk people with atherosclerosis. Studies are being conducted to find out if diet or probiotics could reduce the risk of atherosclerosis. The Mediterranean diet is also very beneficial. A new era of therapy could directly target the intestine in order to control the development of atheromatous plaques.

Schizophrenia affects around 0.7% of the world’s population. This psychiatric disease is characterized by delirium and hallucinations, social isolation, and psychological disruption. Onset is most often in adolescence or young adulthood, between ages 15 and 25.

The gut-brain axis involved?

Schizophrenia is very often accompanied by gastrointestinal disorders. In fact the likelihood of experiencing psychiatric diseases such as schizophrenia may be related to chronic intestinal inflammation involving the immune system. The origin may be an imbalance in the intestinal microbiota (intestinal flora) that favors this inflammation. Disruptions in the microbiota have been found in schizophrenic patients, associated with an increase in intestinal permeability (bacteria and other substances that pass into the blood stream through the intestinal wall). These studies seem to indicate a key role played by the gut-brain axis in the development of the disease.

Acting on the composition of the microbiota

With these results, prevention and treatment options emerge: one of them being rebalancing the microbiota to reduce chronic inflammation. Studies have shown that the administration of probiotics can have anti-inflammatory properties by affecting the immune reaction, although to date, no treatment of this type has demonstrated its effectiveness on schizophrenia.

Mood disorders are common: 300 million people in the world suffer from depression and 60 million have bipolar disorder.These disorders cause mental distress that can often be severe, which can lead to suicide. They are the #1 cause of professional and social disability in the world.

Inappropriate stress response

Each individual has their own vulnerability to depression or bipolar disorder, which is in part genetic.As a result, during unpleasant life events, some people experience an excessive response, with overly elevated secretion of the stress hormones cortisol and adrenaline. This situation can lead to nervous exhaustion and favor the onset of a depressive state. Recent research has also documented the role of intestinal flora (microbiota) in these inappropriate stress responses. Indeed in animals, microbiota participates in the regulation of emotions through communication between the intestine and the brain. In the case of dysbiosis (disruptions in the composition of the microbiota), this regulation is less effective and favors the onset of mood disorders.

A new avenue for treatment

Beyond classic treatments (antidepressants, mood regulators, psychotherapy, etc.), a new avenue is opening: rebalancing the microbiota to influence mood. A recent study also showed that taking probiotics daily, a combination of lactobacilli and bifidobacteria, improved mood and reduced the level of anxiety in healthy subjects.

Anxiety disorders, which include phobias, generalized anxiety disorder, obsessive-compulsive disorder, and post-traumatic stress, are characterized by both physical symptoms (tremors, palpitations, digestive spasms) and mental symptoms (anxious anticipation, hypervigilance, etc.). Fourteen percent of the European population is affected by this illness.

Microbiota activity as a regulator

The gastrointestinal microbiota plays a role in regulating anxiety symptoms related to stress through the microbiota-gut-brain axis. Recent data from humans in good health confirms hypotheses formulated with mice, suggesting that the microbiota influences mood and anxiety.

Stomach-brain paths of interaction

Intestinal microbiota-brain interactions involve the neurological pathway, through the activation of the vagus nerve and the onset of anxious signs (a knot in the stomach), and the blood, through the transportation of molecules from the intestine to the brain. The relevant molecules have several origins: bacterial molecules able to cross the lining of the brain (meninges), molecules secreted by intestinal cells (neuropeptides), and pro- or anti-inflammatory molecules (cytokines) produced by the intestine’s defense system.

New avenues for treatment

Beyond traditional treatment for anxiety disorders (psychotherapy, phytotherapy, anxiolytics, etc.), connections between the gastrointestinal microbiota and the brain are opening new avenues for treatment, such as probiotics, which aim to change the composition of the microbiota. However, the clinical effectiveness of this approach still remains to be proven.

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ASDs include autism, of course, but also Asperger syndrome, Landau-Kleffner syndrome, and PDD-NOS (pervasive developmental disorder not otherwise specified).

Boys affected 4 times as much as girls

Around the world, autism-spectrum disorders affect around one child in 160,2 and affect boys 4 times as often as girls. In spite of the diversity of the disorders, ASDs have characteristics in common: communication problems, alterations in social relationships, limited interests, and behavioral problems.

Indicative signs to watch for

Certain indicative signs should lead to consultations: a child who is indifferent to the sounds around them, who does not point with their finger, who avoids eye contact, who doesn’t react to separations or reunions, whose motor activities are limited and repetitive, etc. Only a specialist can suggest or eliminate an ASD diagnosis and help you tailor treatment.

Causes still unknown

Although the causes of autism-spectrum disorders remain unknown, researchers have closely studied the causes related to genetic or environmental factors. Clinical studies have, furthermore, shown the existence of dysbioses in autistic children,5 associated with a change in metabolic activity in the intestinal microbiota.

No treatment to date

This discovery leads to the idea that correcting imbalances in the digestive ecosystem could improve behavioral anomalies in ASDs and open new therapeutic perspectives. Clinical studies targeting the biological connections between autism and intestinal microbiota are being evaluated. To date, no medication cures autism-spectrum disorders; treatment tailored to the child’s needs can, however, considerably improve their quality of life.

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