“…accelerated


impaired muscle protein synthesis, drives the catabolic response. It would therefore seem logical to target suppressing the accelerated


breakdown with nutritional and metabolic therapy.” rate of muscle protein


More information on why ailing individuals are more prone to loss of body protein


Recall from the text above that loss of body protein is a natural phenomenon between meals that serves to mobilize protein to other areas of need. However, in the healthy situation this is of no clinical significance since the next meal effectively repletes what was previously lost. Unfortunately, in ailing populations the protein losses are accelerated to the point where repletion is sometimes very difficult. The following quotes elaborate on this nature of this ebb and flow:


“There is normally a net breakdown of muscle protein and release of amino acids into the blood in the post- absorptive state. This response provides EAAs to tissues and organs that are so central to physiological function that even short periods of net loss of protein would have adverse consequences. When EAAs become available in the blood after consumption of dietary protein, the loss of muscle protein is reversed to replete what was lost in the post-absorptive state. The periodic loss and gain of muscle protein throughout the day is a normal physiological


catabolic state amplifies this normal response to provide a greater supply of EAAs for the functions required in the catabolic patient not normally encountered such as acute phase protein synthesis, wound healing and immune function.”


Before continuing please note again the last sentence of the above quote, particularly the phrase “acute phase protein synthesis.” What are acute phase proteins? They are inflammatory mediators such as C-reactive protein. As we all know, the vast majority of our chronically ill patients demonstrate chronic inflammation as seen by elevated levels of C-reactive protein and other indicators such as white cell count, liver enzymes, etc. Where does the protein come from to create these increased levels of inflammatory mediators? As noted in the quote above, the source is muscle. Furthermore, if your chronically ill patient has increased need for wound healing or increased immune function due to infection (Lyme’s disease, etc.), protein will also be taken from muscle to serve this need. This is why your chronically ill patient will have accelerated loss of muscle mass to the point where it cannot be restored with the usual dietary intake. In addition, as suggested in the following quote, this accelerated loss of muscle mass will make it more difficult to resolve chief complaints no matter what the clinical presentation:


“The extent of loss of muscle mass in critical illness is related to poor survival and slow return to normal function after recovery.”


In short, the loss of muscle mass is an adaptive response that becomes detrimental when it goes on too long: “…it is provocative to consider that the accelerated


28 response. The accelerated loss in the


muscle


protein


breakdown, and not


breakdown of muscle protein in the catabolic state is an initially adaptive response which becomes counter- productive over time as muscle mass is depleted.”


Furthermore: “The distinction between the clearly adaptive nature of the normal daily loss of muscle protein in the post- absorptive state as compared to the accelerated loss of muscle protein in the severely catabolic state is that the normal loss of muscle protein is balanced by the net gain of muscle protein in the post-prandial state. The overall result of the normal cycling between periods of net loss and net gain of muscle protein is a relatively constant amount of muscle mass over time. In the catabolic state, the rate of loss of muscle protein may be accelerated to the point where it becomes physiologically detrimental.”


Compounding the problem is the fact that, when the patient reaches a certain point of catabolic physiology, the body will start to become resistant to the anabolic effects of dietary protein: “…there is a resistance to the ability of dietary protein to replete the muscle protein in the catabolic state.”


The net result is the following: “Thus, what is a short-term adaptive response of muscle protein to the normal pattern of food intake becomes a liability in stressed patients who cannot maintain a balance between muscle protein synthesis and breakdown over the course of the day.”


The inability of sick people to restore muscle protein with the usual dietary protein intake is referred to as “anabolic resistance”: “The failure of nutritional support to elicit the normal anabolic response is generally referred to as ‘anabolic resistance’.


in accelerated rate of loss of muscle protein in catabolic states.”


Anabolic resistance plays an important role


EVIDENCE THAT FEEDING PROTEIN AND/OR AMINO ACIDS WILL ASSIST IN THE OPTIMIZA- TION OF MUSCLE MASS Is optimization of protein/amino acid intake in ailing individuals a solution to the accelerated loss of muscle mass? To answer this question, please consider another paper co-authored by Wolfe, “Proteins and amino acids are fundamental to optimal nutrition support in critically ill patients” (Weijs PJM et al. Critical Care, Vol. 18, No. 591, published online 2014). In the conclusion of this paper the authors state: “…proteins and amino acids are fundamental to recovery and survival, not only to preserve active tissue (protein) mass but also to maintain a variety of other essential functions. The scientific recognition of the importance of protein is growing, and although optimal protein dosing studies are not available, expert opinion supports administering in excess of 1.2 g/kg/day.”


Of course, as those of you who regularly treat chronically ill patients may have noticed, it can be very difficult to get the average chronically ill patient to ingest that amount of protein through diet alone. This is where protein and amino acid supplementation enters the picture.


(Continued on page 33) THE ORIGINAL INTERNIST MARCH 2018


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