Exercise training and nutritional supplementation, combined with traditional therapy, are promising therapeutic strategies to treat clinical signs of malnutrition and their negative effects in CHF patients.
4.2. Nutritional Supplementation.
Because data suggest that CHF-induced hypercatabolic syndrome causes body protein and AA altered metabolism, the exogenous supplementation of these molecules could be a valid therapeutical strategy to use in CHF patients. However, data also show that improvement of the metabolic and nutritional status of muscle-depleted CHF patients occurs only when adequate energy-protein intake is combined with a specific mixture of all free forms of essential AA (EAA) in a stoichiometric ratio [
19]. In addition, recent studies indicate that free EAA mixture supplementation promotes both more muscular protein synthesis and plasma anabolic and anti-inflammatory protein expression in the elderly than whey proteins. [
20,
21,
22]. These observations could have several explanations.
Firstly, food proteins must be digested by pancreatic enzymes and then the resulting AA would be absorbed by the intestine and introduced into the bloodstream to be transported to cells. As recently shown in aged and/or in diseased patients’ pancreas exocrine efficiency and intestinal metabolism are progressively reduced with consequent altered digestion and the absorption of food components. On the contrary, free AAs do not need to be digested, but are rapidly absorbed and are immediately available in the blood for protein syntheses [
15,
20].
Secondly, from a nutritional point of view, AAs are classified as EAAs, which cannot be synthetized in the body and are therefore needed in the human diet, and non-essential (NEAAs) which can be produced in the body according to the metabolic need so that their presence in the diet is not strictly necessary. Unfortunately, we should note that no dietary proteins have an EAA/NEAA ratio > 0.9, whereas, conversely most proteins have a <0.7 ratio at best.
Interestingly, experimental data show that special EAA mixtures with an EAA/NEAA ratio >1 increases lifespan [
23] and albumin [
24], and also reduces inflammation in healthy mice [
25,
26]. This would suggest that NEAA are not indispensable for cell life and that they are synthesized according to metabolic needs if adequate amounts of EAA are provided. Indeed, only EAA have the metabolic characteristics illustrated below.
Only EAA counteract IRS effects by activating glucose transport and protein synthesis [
13]. These effects occur because EAA mixtures flowing through portal vein is the signal for IGF-1 (Insulin-like Growth Factor-1) secretion [
13], which is the somatomedin responsible to activate anabolic growth hormones (GH) [
13].
It has also been demonstrated that only certain EAA [i.e., branched AA, leucine and/or its ketoacid as beta-hydroxy-beta-methyl butyrate (HMB)] as well as EAA mixture, directly influences protein synthesis stimulating the regulatory intracellular mTOR system [
27,
28,
29]. However, it has been demonstrated that only EAA mixtures formulated according to human needs actually improve energy production and synthesis of oxygen free radicals’ scavengers by mitochondrial biogenesis [
25]. In addition, only EAA mixtures, but not ketoacids (i.e., HMB) and/or certain individual free AA (i.e., Leucine), can provide sufficient concentration of AA to support protein synthesis and provide adequate amount of nitrogen essential for nitrogenous base production. These are indispensable part of ATP and/or of NAD-NADH synthesis, which are crucial to maintain cellular redox homeostasis [
9]. Finally, EAA can also influence the insulin effects on adipocytes enhancing glucose transport and modulating the use of FFA [
9].
Because of all these observations, we can conclude that oral supplementation with special mixtures of free EAAs in a stoichiometric ratio, and formulated according to human metabolic needs, should be regularly used in CHF patients to contrast malnutrition and sarcopenia, up to muscular wasting and cachexia.
However, although from a physio-pathological point of view, the combination of exercise and nutritional support with AAs has solid rational foundations, the relationship itself is very complex. Experimental and clinical data available are quite contradictory and controversial. These mixed results can be partly interpreted by taking into account the experimental models used as the type of exercise (resistance or force), the different nutritional supplementations (food proteins, AAs mixtures, ketoacids with or without micronutrients as vitamins and/or ions), the age of patients studied as well as the presence of comorbidities [
30].
It should be emphasized that nutritional therapies may substantially influence human metabolism. Human metabolism is a complex phenomenon characterized by chemical changes that take place in the cell following an intricate network of specific metabolic pathways, which govern physical processes that determine the cell’s physiology and biochemical properties.
EAA-related metabolism is the sum of all chemical reactions in which one specific chemical compound is transformed through a series of steps into other molecules. Each step is facilitated by a specific co-factor (i.e., vitamins, ions and others). The consequence of nutritional metabolic therapeutical approaches is that nutrition should provide not only one molecule, but all the most fundamental molecules involved in anabolic EAAs-mediated pathways [
9,
31].
This approach has been confirmed in our recent clinical study. This showed that one specific mixture of EAAs efficient to match human metabolic needs has best effects in patients with CHF-induced hypercatabolic syndrome with proteins disarrangement (anaemia) when it is administered with co-factors (vitamin D, B6 and B9, iron) fundamental for the activation of the anabolic pathways of haemoglobin synthesis [
32].
Moreover, recent data shows that altered intestinal function as dysbiosis and increased permeability are present in patient with CHF and they negatively affect patients’ nutrition [
11]. A recent exhaustive review paper supports our perspective. It analyses the effect of different micronutrients proposed to influence cardiovascular risk. An evaluation of the literature would indicate that not all nutritional molecules are equal, given that the needs of patients may well be different. As a result, more personalized and specific integrate dietary interventions involving combinations of beneficial supplements in specific amounts may be needed to stimulate specific anabolic pathways [
33]. Last but not least, it is necessary to distinguish between being fed, with or without nutritional supplementations, and nutrition itself.
Being fed means furnishing food and oral supplementations for the maintenance/improvement of the body’s metabolism. On the contrary, nutrition is the sum of biochemical and physiological complex processes by which a human being either digest, absorbs and metabolizes the macro-micronutrients introduced by ingestion. These data and observations suggest that personalised, functional and integrate nutritional therapies, which consider all salient aspects of nutrition and exercise, should be used to perform best and avoid contrasting data.