in the following description , numerous specific details are given to provide a thorough understanding of embodiments . the embodiments can be practiced without one or more of the specific details , or with other methods , components , materials , etc . in other instances , well - known structures , materials , or operations are not shown or described in detail to avoid obscuring aspects of the embodiments . reference throughout this specification to “ one embodiment ” or “ an embodiment ” means that a particular feature , structure , or characteristic described in connection with the embodiment is included in at least one embodiment . thus , the appearances of the phrases “ in one embodiment ” or “ in an embodiment ” in various places throughout this specification are not necessarily all referring to the same embodiment . furthermore , the particular features , structures , or characteristics may be combined in any suitable manner in one or more embodiments . the headings provided herein are for convenience only and do not interpret the scope or meaning of the embodiments . the compositions according to the invention ( in the following referred as aa - compositions ) comprise — as main active ingredients — the branched amino acid leucine in combination with at least one of , and preferably both , the branched amino acids isoleucine and valine . the preferred molar ratios of isoleucine and valine , with respect to one mole of leucine , are as follows : isoleucine : from 0 . 2 to 0 . 7 , preferably from 0 . 4 to 0 . 6 ; valine : from 0 . 2 to 0 . 8 , preferably from 0 . 4 to 0 . 7 . the inventor ascertained that the activity of the mixtures grew after adding at least one of , and preferably both , the amino acids threonine and lysine to the branched chain amino acids . more in detail , the preferred molar ratios of these amino acids , with respect to one mole of leucine , are as follows : threonine : from 0 . 15 to 0 . 50 , preferably from 0 . 2 to 0 . 45 ; lysine : from 0 . 15 to 0 . 60 , preferably from 0 . 3 to 0 . 55 . in particular , currently , the studies carried out by the inventor have demonstrated that the more efficient compositions are those in which , considering the sum of leucine , isoleucine and valine equal to 1 , in the abovementioned stoichiometric ratio , then the sum of threonine and lysine is comprised between 0 . 10 and 0 . 50 ( i . e . 1 : 0 . 10 - 0 . 50 ), still according to the molar weight , preferably between 0 . 25 and 0 . 45 ( i . e . 1 : 0 . 25 - 0 . 45 ). studies carried out by the inventor have further shown that such compositions are more active in presence of further one or more essential amino acids selected from histidine , phenylalanine , methionine and tryptophan . considering the sum of leucine , isoleucine , valine , threonine and lysine equan1 to 1 , then the overall amount of the further essential amino acids may vary between 0 . 02 to 0 . 25 ( i . e . 1 : 0 . 02 - 0 . 25 ), preferably from 0 . 05 to 0 . 15 ( i . e . 1 : 0 . 05 - 0 . 15 ), still intended as the molar ratio . the sum of the amount of threonine and lysine , still on the basis of the molecular weight , is preferably lower with respect to the sum of the single amounts of branched amino acids used , but greater with respect to the sum of the amount of the further essential amino acids used in the mixture . furthermore , still preferably and on a molecular weight basis : the amount of lysine is lower with respect to single amounts of the branched amino acids , but greater with respect to the single amounts of each of the further essential amino acids used in the mixtures ( and hence even greater than the sum of the single amounts of such further essential amino acids , not considering threonine thereamong ); the amount of threonine is lower with respect to the single amounts of lysine and of the branched amino acids , but greater with respect to the single amounts of the further essential amino acids used in the mixtures , and much more preferably greater than the sum of the single amounts of the further essential amino acids . in case methionine is used , the activity of the mixtures may be further enhanced by also providing for the insertion of the non - essential amino acid cystine ( and / or cysteine ) into the composition , in an amount of moles at least equivalent to that of methionine , and preferably comprised between 150 and 350 % of methionine . alongside the abovementioned amino acids the aa - compositions described herein may also comprise the non - essential amino acid tyrosine , whose ideal amount shall be comprised between 15 and 50 %, preferably between 20 and 35 %, of the amount of phenylalanine in moles . though the aa - compositions may possibly comprise other amino acids with respect to the ones described above , the overall amount of said other amino acids shall not exceed 20 % of the total of the active ingredients , and / or not exceed 10 % per each single said other amino acid ( still in molar weight ). furthermore , in particular , when preparing the aa - compositions according to the invention , the amino acids serine , proline , glycine , alanine , glutamic acid and , above all , arginine , are preferably avoided , given that they can be counterproductive or even harmful in some concentrations or stoichiometric ratios with the said formulation . the amino acids used in the experimentation that led to the identification of the indicated ratios are those of the levogyrous type , corresponding to those present in nature and which are thus to be considered the preferred active form . however , the inventor ascertained that also the racemic form may perform the same activity , though in a lower manner proportional to the d - form percentage . also the active derivatives of the indicated amino acids , in particular the salts thereof , shall obviously be deemed falling within the scope of the present invention . further specifications , in terms of amounts and ratios among the various amino acids provided for by the compositions for prevention and / or treatment of renal diseases are contained in the attached claims , which form an integral part of the technical teaching provided herein in relation to the invention . though expressed on the basis of molecular weight ( i . e . in moles ), the ratios indicated are applicable , in general terms , also in case of calculation according to the weight in grams of the various amino acids indicated ( however bearing in mind that the amount of lysine , expressed in grams , may then be greater with respect to the single amounts of isoleucine and valine ). in the aged kidney , progressive glomerulosclerosis , and reduced glomerular filtration rate , all occur concomitantly with the loss of functioning nephrons , so that elderly kidneys are more susceptible to failure when other insults are superimposed . the main findings of the instant description in the kidney after prolonged aa - composition intake in m - aged animals were 1 ) very scarce fibrosis limited to the interstitium and glomeruli ; 2 ) increases in glomerular perfusion markers such as enos and vegf and 3 ) recovery and / or maintenance of renal function also in elderly subjects . to better understand the renal effects of dietary aa - composition intake in middle - aged rats the present inventor assessed changes in the glomerular , and tubular compartments with a combined morphological / morphometric , histochemical , and immunohistochemical approach . the present inventor demonstrated in the instant description that in m - aged rats chronic aa - composition supplementation prevents the onset of morphological changes during the early stages of senescence . in particular , by using high - resolution morphometry on semi - thin sections reduced glomerular tufts was detected in the m - aged group that were restored after aa - composition supplementation to the form in younger rats . in conclusion , the present data show that prolonged administration of a aa - composition have beneficial effects on kidney metabolism of m - aged rats , mainly retarding the typical alterations seen in senescence . aa - composition supplementation in the diet is a new strategy for maintaining a healthy renal status to prevent renal disorders and improve the quality of life . the experimental protocol was approved and conducted in accordance with the italian ministry of health and complied with the the national animal protection guidelines . seventeen male wistar rats were used : 5 young ( 2 - month - old ) animals , and 12 middle - aged ( m - aged ; 18 - month - old ) animals . the animals were caged separately . m - aged animals were divided into 2 groups : control group ( m - aged , n = 6 ) and aa - composition treated group ( m - aged + aa , n = 6 ). the animals were placed in a quiet room with the temperature and humidity controlled . a 12 / 12 - h light / dark cycle was maintained ( lights on from 7 a . m . to 7 p . m .). the rats were fed a standard diet ad libitum ( 18 . 8 % protein content ; dottori piccioni , gessate , milan , italy ) with water ad libitum ( control m - aged and young groups ) or a diet supplemented with aa - composition in the form of a solution ( m - aged + aa group ) that provided 1 . 5 g / kg per day of aa - compositions in the drinking water for 90 days . the concentration of the aa - composition in the drinking water was adjusted to the average daily water consumption of the rats ( about 25 ml ) and mimicked the recommended daily dose for humans ( 1 ). the composition of aa - composition used in the present experiments is shown in table 1 . the body weight and water or aa - composition consumption of each animal were monitored daily . at the end of the treatments , the animals were killed under deep ether anesthesia . the kidneys were quickly removed and placed in an ice - cold saline solution . the samples used for histochemical analysis were carefully mounted in tissue - tek ® oct ( sakura finetek europe , the netherlands ) embedding medium before they were frozen in liquid nitrogen and stored at − 80 ° c . the composition of aa - composition used in the present experiments is shown in table 1 . as observable from table 1 , the weight ratios between leucine , isoleucine and valine are preferably equivalent to 2 : 1 : 1 . table 1 and table 2 also show that the single amounts ( weight in grams or moles ) of histidine , phenylalanine , methionine and tryptophan are preferably decreasing ( i . e . the amount of histidine is greater than phenylalanine , which is greater than methionine , which is greater than tryptophan ) and the amount ( weight in grams or moles ) of cystine ( and / or cysteine ) is preferably greater than tyrosine . the present inventor performed a study — during a period of 20 months — directed to assess the renal function as blood urea nitrogen ( bun ) by the reflotron test ( roche diagnostics , indianapolis ). blood samples of control rats ( control group ) and rats supplemented with aa - composition ( aa - treated group ) for bun determination were collected at different time intervals after cisplatin injection . bun levels exceeding 30 mg / dl were considered abnormal . rats were from charles river , italy and the treatment was performed in accordance with the international guidelines . male rats of 4 months were caged separately and divided in 2 groups ( control and aa - composition treated group ) of 40 animals each . the rats were fed a standard diet ad libitum ( 18 . 8 % protein content ; dottori piccioni , gessate , milan , italy ) with water ad libitum ( control group ) or a diet supplemented with aa - composition in the form of a solution ( aa - treated group ) that provided 1 g / kg / day of aa - composition in the drinking water for 20 months . the composition of aa - composition used in the present experiment is shown in table 1 . the body weight and water or aa - composition consumption of each animal were monitored daily . one kidney from each animal were removed , fixed with 3 % glutaraldehyde in pbs ( ph 7 . 4 , 0 . 1m ), and postfixed for 1 hour with 1 % oso 4 in the same buffer . the samples were processed with standard procedures for embedding in araldite ( sigma chemical co , milan , italy ). thick sections ( about 1 μm ) were stained with toluidine blue . ultrathin sections ( 70 nm ) were stained with a saturated aqueous solution of uranyl acetate and lead citrate and examined with a philips cm10 electron microscope . all measurements were obtained using standard morphometric techniques , as previously described ( 2 , 3 ). the number of glomeruli ( nglo ), the mean area of glomeruli ( aglo ), the mean area of the renal corpuscle ( acor ), and total area of the renal parenchyma ( atot ) were evaluated on thick plastic sections stained with toluidine blue . from glomerular data the ratio between aglo and atot ( aglo / atot ) and the number of glomeruli per unit area , also called the glomerular density ( nglo / mm 2 ) were calculated . collagen deposition and fibrosis were evaluated by a sirius red staining method using a modified picrosirius procedure as previously described ( 4 ). briefly , the sections were deparaffinized , rehydrated in distilled water , and immersed in 1 % phosphomolybdic acid ( sigma - aldrich , st . louis , mo ., usa ) for 5 min and then covered with 0 . 1 % ( w / v ) sirius red f3b ( c . i . 35780 science lab , huston , tex ., usa ) in saturated picric acid solution for 1 h at room temperature . the sections were then washed in water and rapidly dehydrated , cleared in xylene , and mounted . all sections stained with sirius red were analyzed using a light microscope ( olympus bx50 , tokyo , japan ) under normal light and polarized light obtained with a polarizer filter ( olympus u - ant , tokyo , japan ) in order to analyze the initial collagen organization and the fibrosis , respectively . under these conditions , collagen fibres of different thickness are coloured differently . whereas the birefringent ( anisotropic ) colour is more a measure of collagen fibre size than of collagen type , usually the thicker and denser type i collagen fibres are detected as orange to red , whereas the thinner type iii collagen fibres appear yellow to green ( 5 , 6 ). immunohistochemistry . sections were incubated overnight with primary anti - inos ( nos2 - n20 - sc651 ), anti - enos ( nos3 - c20 - sc654 ), or anti - vegf ( c - 1 - sc7269 ) polyclonal antibodies from santa cruz biotechnology inc . ( santa cruz , calif ., usa ) diluted 1 : 100 with pbs . the sections were processed in accordance with the manufacturers &# 39 ; protocols , visualized with a rabbit abc - peroxidase staining system kit ( santa cruz biotechnology ), and mounted with dpx . the reaction product was visualized using 0 . 3 % h 2 o 2 and dab at room temperature . the immunohistochemistry control was performed by omitting the primary antibody in the presence of isotype - matched iggs . to exclude incorrect interpretation of the immunostaining due to the presence of endogenous biotin ( 7 ), the present inventor also carried out experiments using the peroxidase - anti - peroxidase detection system , but obtained similar results . each set of experiments was done in triplicate , with each replicate always carried out under the same experimental conditions . the staining intensity on both histochemical and immunohistochemical slides was evaluated using an optical olympus bx50 microscope equipped with an image analysis program ( image pro plus , immagini e computer , milano , italy ) and analyzed quantitatively . the integrated optical density ( iod ) was calculated for arbitrary areas , by measuring 10 fields for each sample using a 40 × objective . data were pooled to obtain a mean value , and a statistical analysis was applied to compare the results obtained from different experimental groups . morphometric data are expressed as mean ± sd unless otherwise stated . the statistical significance of the differences between means was assessed with one - way anova followed by the student - newman - keuls test or with a student t - test . a probability of less than 5 % ( p & lt ; 0 . 05 ) was considered significant . to test the effect of aa - composition on renal health , the diet of m - aged rats was supplemented with aa - composition dissolved in drinking water . young and m - aged rats fed a standard diet were used as controls . at the end of the treatments , the young animals were 5 months old and the m - aged animals were 21 months . body weight , kidney weight , and mean daily consumption of water and aa - composition in form of solution are summarized in table 3 . no significant differences in body or kidney weight between m - aged and m - aged + aa animals were observed ( table 3 ). the water and aa - composition intake did not differ between groups . the present inventor did not observe any significant differences of glomerular number ( nglo / mm 2 ) among groups . however , m - aged rats had significantly smaller glomeruli ( aglo ), reflected in a reduction in aglo / atot of about 40 % relative to young rats . animals in the m - aged + aa group were not statistically different from young animals on these measures ( fig1 ). sirius red staining . the m - aged animals occasionally showed signs of interstitial fibrosis and glomerulosclerosis of moderate intensity . in contrast , the m - aged animals supplemented with aa - composition of table 1 did not show these morphological signs of incipient senescence . immunohistochemical staining for various markers in the three experimental groups were performed . the values are summarized in table 4 , wherein integrated optical density values (± sd ) in the three experimental groups are reported . m - aged animals showed significantly lower vegf expression relative to young animals . in particular , the glomerular endothelia and bowman &# 39 ; s capsule cells of m - aged animals did not show vegf expression . in contrast , the animals supplemented with aa - composition of table 1 showed intense vegf expression mainly in glomeruli and to a lesser extent inside the bowman &# 39 ; s capsule cells ( fig2 ). endothelial nitric oxide synthase ( enos ). inside the tubular cells of young animals , enos expression was very strong . in the m - aged animals , enos expression decreased , whereas aa - composition supplementation restored the intense immunostaining in the tubular compartment to levels similar to those in the young group . no or very faint immunostaining was seen inside the glomeruli in all experimental groups ( fig3 ). young animals showed intense inos expression only in some cells of the distal tubules , whereas animals in the m - aged group showed increased expression in glomeruli and in the distal and proximal tubules . m - aged animals supplemented with aa - composition showed intense inos expression restricted to cells of the distal tubules and , as in young rats , no expression was seen inside the glomeruli or in other tubular cells ( fig4 ). the present inventor observed a decrease of renal function of the control group during the 20 month period of treatment ( t 0 to t 4 ), i . e . an increase of bun , while the aa - treated group surprisingly maintained renal function within the limits ( bun & lt ; 30 mg / dl ). the data ( expressed an mean ± sd ) are reported in table 5 . at the end of the treatments , the animals were 24 months - old .
composition comprising leucine , isoleucine , valine , threonine and lysine for use in prophylactic and / or therapeutic treatment of renal disorders in a subject , preferably an elderly subject .