CHAPTER V
PATHOLOGY OF GOUT—PROTEIN METABOLISM
Not only is the proximate cause of gout unknown, but the essential nature of the disease is still shrouded in obscurity; for the obliquity in trend of protein metabolism, manifested though it be by striking phenomena, is clearly only the outcome of some, as yet undetermined, derangement in the mechanism of intermediary metabolic or bio-chemical change.
This is, of course, but to restate the problem we are confronted with. Wholly to solve the enigma would postulate ability on our part to trace ingested foodstuffs through all their vicissitudes from the moment of entry into the blood or lymph-stream till flung out as effete matter through the various avenues of excretion; but, unhappily, we know the story only in part, its beginning and end, but not what lies between.
We know much of the complex changes that take place in food prior to absorption, and of the modus operandi of the latter not a little. Comparably, too, we can gauge the quality and quantity of end-products, the chemical outcasts, as they escape in the urine, sweat or breath, and largely how achieved; but of the intermediate steps between absorption and excretion we catch but a glimpse here and there. The sequestered path by which the inanimate molecules of food uprise to Life, and anon go down to decay and death, are still hidden.
In other words, little do we know of the relationship of labile, or food-protein, to tissue protein. True, the coarse fact of abnormal protein loss in renal disease may be revealed in the urine, as likewise the waste of albumoses in myeloma, etc., and the incidence of amino-acids in disease of the liver. Similarly, the appearance of cystin or of alkapton in the urine bespeaks flaws in protein metabolism, failures in the normal disruption of amino-acids. All these are of the grosser anomalies of protein metabolism, but more subtle those of gout!
Complex, in truth, the problem here presented, than which none more subtle exists in the realm of bio-chemistry. True, quantitative variations in the content of the urine as to urea, uric acid, etc., undoubtedly bear a direct relation to protein metabolism, but they give us little, if any, substantial clue as to the particular metabolic warp responsible. We see this particularly in regard to uric acid, so long accredited with an essential rôle in gout.
Thus we cannot, on the basis of the variations in its excretion only, presume to diagnose “gout.” This because even more extensive variations occur in healthy persons. On the other hand, attacks of gout never occur when urates are absent from the blood. To reduce the amount of these urates is clearly then of importance, and obviously to this end a knowledge of their source is essential. We have an analogy to hand in diabetes, in which the somewhat similar problem relating to glycosuria has been partially solved.
Revelations of the Bio-Chemist
But before proceeding to the more strictly biological aspect of the relationship of uric acid to gout, we must, as in the study of any other problem of metabolism, place ourselves in possession of the main facts relating to the chemistry of protein, and more particularly of purin or nuclein metabolism; for it was just this same lack of even the most rudimentary facts, especially regarding the chemistry of uric acid, that vitiated the conclusions arrived at by the earlier workers in this sphere. Disabilities of technique of necessity rendered inaccurate the results obtained by these pioneers in research, while the significance of the facts they laboriously gleaned was likewise misinterpreted.
But with the advent of highly trained organic chemists, well skilled in the investigation of bio-chemical problems, a basis of accurate chemical facts was established. The story of the fate of protein and purin substances in the animal body, at one time a medley of guesses and gaps, was brought to one of relative certitude and completeness. The change involved has proved in truth revolutionary, and many the cherished shibboleth that has been ruthlessly cast aside.