Diabetoiogia 9 Springer-Verlag 1985

Transcription

1 Diabetlgia (1985) 28: Diabetigia 9 Springer-Verlag 1985 The effects f physical training n insulin secretin and effectiveness and n glucse metablism in besity and Type 2 (nn-insulin-dependent) diabetes mellitus M. Krtkiewski, P. L6nnrth, K. Mandrukas, Z. Wrblewski, M. Rebuff6-Scrive, G. Hlm, U. Smith and P. BjOrntrp Departments f Rehabilitatin Medicine and Plastic Surgery and the Clinical Metablic Labratry f Departments f Medicine I and II, Sahlgren's Hspital, University f GStebrg, G6tebrg, Sweden Summary. Obese subjects with nrmal glucse tlerance (n = 55), and, in anther study, a grup f patients with Type 2 (nn-insulin-dependent) diabetes (n=33), and cntrls (n= 13) matched fr bdy weight and age but with nrmal glucse tlerance, participated in an individualized physical training prgram fr 3 mnths. Under cntrlled dietary cnditins, metablic studies were perfrmed befre and in steady state after the last exercise sessin after training in the subjects shwing signs f physical training in VO2 max and heart rate measurements. N changes ccurred in bdy weight, bdy cell mass, bdy fat r adipse tissue cellularity. Oral glucse tlerance was imprved in the patients with diabetes mellitus nly. In bth diabetic and cntrl subjects initially elevated C-peptide cncentratins decreased, while lw C-peptide values increased and which was particularly prnunced in diabetic subjects with subnrmal values. Peripheral insulin values did nt change. Glucse dispsal rate measured with the glucse clamp technique was similar in diabetic patients and cntrl subjects. An imprvement was seen at bth submaximal and maximal insulin levels in bth grups, crrelating with imprvement in glucse tlerance in the diabetic subjects. N changes were fund in adipcytes in insulin binding r the antiliplytic effect f insulin at submaximal insulin levels, but there was a nrmalizatin f a decreased glucse incrpratin int triglycerides. These results indicate that bth insulin secretin and effectiveness are altered by physical training in different ways in different clinical entities. They suggest that in insulin resistant cnditins with high insulin secretin (as indicated by high C- peptide cncentratins) the increased peripheral insulin sensitivity is fllwed by a decreased insulin secretin. This is nt assciated with an imprvement f glucse tlerance. In Type 2 diabetes with lw insulin secretin, an increased insulin secretin results frm physical training, perhaps due t accmpanying sensitizatin f the autnmic nervus system. Peripheral insulin cncentratins are nt altered, suggesting that the extra insulin prduced is captured by the liver. This mechanism, as well as the imprved peripheral insulin respnsiveness seen in the whle bdy and als seen at the cellular level, prbably bth cntribute t an imprvement in glucse tlerance. Key wrds: Type 2 diabetes, besity, physical training, glucse tlerance, insulin, C-peptide, glucse damp, insulin binding, adipcytes. By traditin exercise is ne f the basic principles in the therapy f diabetes mellitus t stabilize glucse hmestasis and t imprve diabetic cntrl. The dcumentatin f such effects is, hwever, surprisingly incmplete. Only recently have well-cntrlled studies been perfrmed with the purpse f trying t better define the place f regular exercise and physical training in the therapy f diabetes mellitus. In general, the effects n glucse metablism have been mderate, f shrt duratin, r even lacking (1-3), in spite f the nw well-established fact that increased levels f plasma insulin are clearly lwered by physical training due t an increased peripheral insulin sensitivity (4). These findings suggest that, at best, nly a subgrup f Type 2 (nn-insulin-dependent) patients benefits frm physical training. In the present wrk this pssibility was elucidated by subjecting sufficiently large grups f diabetic and bese subjects and cntrls t physical training t allw an analysis f effects in subgrups, characterized in terms f glucse intlerance as well as secretin, peripheral uptake and effectiveness f insulin. Changes in these variables were registered after physical training in an attempt t explain hw alteratins in glucse tlerance are brught abut. Subjects and methds Subjects examined Study L Fifty-five bese wmen were recruited frm the Obesity Outpatient Clinic at the University Hspital. They were all in a nn-dieting, weight-stable cnditin, bdy weight changing less than 2 kg

2 882 M. Krtkiewski et al.: Training in diabetes within the preceeding three mnths. They all had a nn-diabetic glucse tlerance test (fr definitin, see belw). Nn-bese cntrl wmen (n= 15) were fund amng vlunteers btained by an advertisement in a lcal newspaper. They were weightstable, healthy and nn-dieting. Mst f these wmen were physically active t sme extent, but nne was training regularly. N subjects were taking cntraceptive drugs r any ther drugs f knwn imprtance fr the examined variables. All the cntrls had nrmal glucse tlerance tests. The bdy cmpsitin and ther characteristics f these subjects are seen in Table 1. Study H. Frty-six subjects, 34 wmen and 12men, were recruited frm the Diabetes r Obesity Outpatient Clinics at the University Hspital r by an advertisement in a lcal newspaper fr participatin in the study. The general characteristics f the patients are summarized in Table 2. The subjects had a histry f weight stability (_+ - 2 kg bdy weight) during at least the preceeding 3 mnths. They were then bserved fr abut tw mnths t ensure weight stability by bdy weight recrdings at least twice during this perid. All were actively emplyed but had a rather sendentary way f life, nt training regularly r being engaged in any kind f sprts activity. Nne was n a diet except patients with knwn Type2 diabetes (12men and 12 wmen). These subjects were als treated with sulfnylurea drugs fr at least 1 year. This medicatin was nt changed during the perid f physical training, and n subject was n insulin treatment. N subject had bvius signs r symptms f diabetic cmplicatins, and the mean diabetes duratin was 5.1 years. Of the 46 subjects participating in study II glucse tlerance tests revealed that 13 had a nrmal glucse tlerance (fr definitin, see belw), while the remaining (n = 33) had decreased glucse tlerance f varying degrees including vert clinical diabetes mellitus (n=24) and were examined in ne grup. Five days prir t, as well as after the physical training perid, the patients were placed n a diet estimated t give calric balance, viz. 35 kcal per kg ideal bdy weight. Ideal bdy weight was taken frm the Metrplitan Life Insurance tables as the mean f the value given at medium frame. The diet cnsisted f abut 15, 40 and 45% f prtein, fat and carbhydrate, respectively, and was identical befre and after the perid f physical training. Glucse tlerance tests and the euglycaemic glucse clamp were perfrmed under these cnditins n the furth day r later after the last exercise sessin. All participants were instructed nt t change their rdinary diet during the training perid. All participants gave their infrmed cnsent befre entering int the examinatins. The study was apprved by the Ethical Cmmittee at the University f Grtebrg. Oral glucse tlerance test (OGT1). One hundred grams glucse, disslved in 200ml lemn flavured water, were taken rally in the mrning in the vernight fasting state. The subjects were asked nt t smke that mrning and arrive t the labratry withut rush. Bld samples were drawn befre and at 30, 60, 90 and 120 min after glucse ingestin frm an indwelling catheter in an antecubital vein fr enzymatic determinatin f bld glucse (GLOX, Kabi, Sweden), plasma insulin and cnnecting C-peptide by cmmercially available radiimmunassaymethds (Phadebas Pharmacia,Uppsala, Swedenand Nv, Cpenhagen, Denmark respectively). The errr f these methds are < 0.05% in the mean range f the analysed results. With this test the subjects were classified as diabetic if at least three glucse values exceeded the ranges prpsed by the Diabetes Data Grup [5]. Bdy cmpsitin determinatins Bdy weight was recrded t the nearest 0.1 kg and height t the nearest cm. Ttal bdy ptassium was measured in a whle bdy cunter, after crrectin fr the shielding effect f bdy fat [6]. Lean bdy mass (LBM) and bdy fat were then calculated as described by Frbes et al. [7]. Subcutaneus needle bipsies f adipse tissue were perfrmed in the epigastric, hypgastric, femral, gluteal and upper arm regins fr determinatins f fat cell weight with a micrscpic methd [8]. These values were averaged. Ttal fat cell number was estimated by dividing bdy fat with the average fat cell weight. Exercise test and determinatin f maximal xygen uptake (V02 max) A Mnark (Varberg, Sweden) mechanically braked bicycle ergmeter was used fr the exercise tests. The maximal xygen uptake measurements were perfrmed by stepwise wrk lad increase until exhaustin [9] with cntinuus ECG and frequent bld pressure recrdings. Expired air was cllected in Duglas bags, and the vlume and O2-cntent measured in a Beckman OM-I 1 instrument during the last minutes f the maximal wrk lad. The test was repeated nce at anther ccasin t ensure reprducibility, which was +3%. Heart rate and bld pressure at predetermined submaximal wrk lads (50 W and 100 W) were als recrded fr cmparisns befre and after the physical training prgramme. Physical training The grups were trained fr 3 mnths, three times a week. The duratin f each training sessin was 50min, starting with 10-15rain warm-up including walking, jgging and calisthenics f light intensity, and including exercises with all parts f the bdy. The prgramme then cntinued with alternating heavy and light perids. The heavy intervals were perfrmed n a bicycle ergmeter, lasted fr 4 min, and were standardized fr each patient t reach 80-90% f the individual VO2 max, cmmencing with a submaximal wrk lad. This level was adjusted upwards as the cnditining f the participants increased during the training t be kept at an 80-90% level. Euglycaemic glucse clamp measurements Arterial bld was drawn frm the radial artery and fed int an autmatic, cntinuus glucse mnitring system (Gambr, Lund, Sweden), which measures the bld glucse levels every minute. A slutin f 0.4 IU/ml f prcine insulin (Actrapid, Nv, Cpenhagen, Denmark) disslved in istnic saline was infused int the subclavian vein thrugh a catheter intrduced int a brachial vein with a cnstant infusin pump (IMED 922 H, San Dieg, Calif., USA). The insulin was given at tw infusin rates (0.08 and 0.60 IU. kg bdy weight -a. min-1). The plasma insulin levels btained by these infusins were nt different befre and after training ( and at lw level and and mu/1 at high level - means + SEM, befre and after training respectively). Bld glucse levels were kept cnstant by the infusin centrally f a 40% (w/v) slutin f glucse cntaining 100 mml/1 f ptassium, 20 mml/1 f magnesium and 30 mml/l f phsphate. Bld fr plasma insulin levels was drawn every 5 min. When steady state was reached, determined by the cefficients f variatin (mean + SD) fr insulin and glucse, the glucse dispsal rate was calculated during the last 20-rain perid f the lw and high insulin infusins respectively. The duratin f each f these perids was 60 min. These studies were perfrmed in a subgrup f 13 cntrl and 10 diabetic subjects wh gave their infrmed cnsent. Adipse tissue studies After fasting vernight, a subcutaneus adipse tissue bipsy was taken frm the hypgastric regin in lcal anaesthesia (Lidcaine, Astra, Sweden). Care was taken nt t infiltrate the tissue t be excised. Insulin binding Fat ceils were liberated by incubating the bipsies in medium 199 cntaining cltagenase (1.5 mg/ml) and 50 g/1 f bvine serum albumin

3 M. Krtkiewski et al.: Training in diabetes 883 Table 1. Characteristics f examined grups (Study I) Age (years) 37.1 _+ 1 Height (cm) Weight (kg) Whle bdy ptassium (Meq) Bdy fat (kg) Cntrl subjects Obese subjects (n=15) (n=55) Befre After training training _ _ (p<.l) 20.0_ _ _ <.l) Means _+ SEM. Cmparisns between cntrls and bese subjects Table 2. Characteristics f examined grups (Study II) Cntrl subjects (n = 13) Diabetic subjects (n = 33) Befre After Befre After Age (years) _ Bdyweight _ _+3.1 (kg) Bdy cell _ _ mass (kg) (p< 0.05) Bdyfat (kg) (p<0.05) Fat cell number (p < 0.05) (101~) Fat cell _ weight (p.g) Means_ SEM. Cmparisns between cntrls and Type 2 diabetic subjects fr 1 h at 37 ~ as previusly described [10]. After filtratin, the cells were carefully washed fur times in fresh medium. Insulin binding t the cells was then measured using the methd f Gamrneltft and Gliemann [11]. The cells were incubated fr 45rain at 24~ with ng/ml mncmpnent 125I-insulin. Cld insulin added was present at the indicated cncentratins. Tracer binding in the presence f 4.17ng/ml ( tU/ml) unlabelled insulin was cnsidered nnspecific and subtracted frm the results. Mean fat cell size was determined accrding t Smith et al. [10]. Mean fat cell surface area was calculated accrding t the frmula: SA= [d2+ SD 2] Jr: where SA= surface area, a = mean fat cell diameter, and SD the standard deviatin. Liplysis and glucse incrpratin int triglycerides After preincubating tissue fragments (average weight 10rag) fr 30 rain, the incubatins were perfrmed fr 2 h at 37 ~ in fresh medium 199 cntaining 1 mml glucse, 40g/1 bvine serum albumin, 0.t5 ~tci/ml (U-14C)-glucse and nradrenaline (10-5 M), and different cncentratins f insulin. Glycerl release t the incubatin medium, analyzed accrding t Laurell and Tibbling [12], was taken as an index f liplysis. Triglycerides were extracted accrding t Dle [13] and the radiactivity cunted. These studies were perfrmed in 12 cntrl and 18 diabetic subjects wh gave their infrmed cnsent. Glucagn-pr insulin was generusly supplied by Eli Lilly and C, (Indianaplis, Ind., USA). Medium 199 was btained frm Star- ens Bakterilgiska Labratrium, (Stckhlm, Sweden). Cllagenase, type I, bvine serum albumin, fractin V, and nrepinephrine bitartrate were frm Sigma (St.Luis, M., USA). U-14C-glucse (4 mci/mml) was btained frm New England Nuclear Crpratin (Bstn, Mass., USA), and ~2SI-mncmpnent insulin (specific activity abut 190 ~tci/ug) was a generus gift frm Dr. S. Ivarssn, Malmr, Sweden. Statistical methds Intra-individual differences, cmparing results befre and after the training perid as well as differences between grups, were tested using the Student's t-test. Results Study I As seen in Table 1, physical training was nt fllwed by any changes in bdy cmpsitin. All subjects fllwing the training prgramme shwed increases in VO2 max. and/r decreases f heart rate n a submaximal wrk lad (nt shwn). Table 3 shws that the fasting glucse values and sum f the glucse values during glucse tlerance test were higher in the grup f all bese subjects than in cntrls (p<0.05). The sum f insulin values during glucse tlerance test was als higher in the bese grup (p< 0.01) but the C-peptide values were nt. Physical training in the entire grup f bese subjects was nt fllwed by any changes in glucse r insulin, while the sum f C-peptide cncentratins decreased. Figure 1 a shws the C-peptide values befre and after physical training (r: 0.72 p< 0.01) and Figure 1 b the crrelatin between the changes in C-pepfide and the pretraining values (r: 0.28, p< 0.05). There were n crrelatins between the changes f insulin and glucse cncentratins with their respective pretraining values (nt shwn). T further analyse this phenmenn the bese subjects were divided int three grups with lw, nrmal r high insulin secretin, utilizing the sum f C-peptide values f the cntrls as dividing line. The bese subjects with C-peptide cncentratins within the mean _+ 2 SD f the cntrls were called nrmal insulin secretrs (NIS), thse belw r abve these limits were lw high insulin secretrs (LIS and HIS grups respectively). As seen in Table 3 these grups did nt differ in glucse tlerance, but the besity HIS grup had higher insulin values than the ther grups (p< 0.05). With physical training n changes ccurred in neither bld glucse nr insulin values in any f these grups. C-peptide values decreased in the HIS grup and NIS grup (nly sum f C-peptide values), and increased in the LIS grup (Table 3). There were n differences in bdy weight, bdy fat and ttal bdy ptassium between the grups and n changes with physical training (nt shwn).

4 884 M. Krtkiewski et al.: Training in diabetes Table 3. Effects f physical training n glucse tlerance and plasma insulin and C-peptide cncentratins (Study I) Cntrl subjects Obesity all Obesity HIS Obesity NIS Obesity LIS (n = 15) (n = 55) (n = 15) (n = 22) (n = 14) Fasting glucse (mml/1) Befre _+ 0.1 After _ p NS NS NS NS Sum f glucse (mml/1) Befre After p NS NS NS NS Fasting insulin (nml/l) Befre ' _ 0.01 After 0.11 _ _ _ p NS NS NS NS Sum f insulin (nml/1) Befre 1.00 :k _ _ After _ _ p - NS NS NS NS Fasting C-peptide (nml/1) Befre 0.32 _ After p NS 0.10 >p> 0.05 NS 0.10 >p> 0.05 Sum f C-peptide (nml/1) Befre 5.11 _ _ After p - p< 0.05 p< 0.05 p< 0.05 p< E lo c LD Z Z,< n," i-. n~ LU ~ E E Z -2 ua l, a. d LL O O ~ ~ ~ <3 -t, -6 SUM OF C-PEPTIDE a BEFORE TRAINING b ( nml / L ) -B Fig. 1. a The relatinship between the sum f plasma C-peptide cncentratins during glucse tlerance test befre and after physical training in bese subjects, y= x; r: 0.72; p< 0.01 (Study I). b The relatinship between the sum f plasma C-peptide cncentratins during glucse tlerance test befre training and the change in these values with physical training in bese subjects, y= x; r: 0.28; p < Shaded area: Mean_ 2 SD f values fr nnbese cntrls (Study I)

5 M. Krtkiewski et al.: Training in diabetes Study H Table 2 shws that age, bdy weight and average fat cell size did nt differ between the nn-diabetic and diabetic subjects. The diabetic subjects had higher bdy cell mass, less bdy fat and fewer fat cells than the nn-diabetic subjects. Nne f these variables changed with physical training. A mean increase was seen in maximal xygen uptake fllwing training, while heart rate and bld pressure decreased bth at rest and during submaximal wrk (Table 4). Examining individual data, five diabetic subjects did nt shw any evidence f physical training in neither VO2 max nr heart rate during submaximal Table 4. Circulatry variables f examined grups befre and after physical training (Study II) Cntrl subjects (n=13) Diabetic subjects (n=33) Befre After Befre After VO2 max b c (l/rain) Heart rate (beats/min) Rest a c Wrk 116 _ _ a (5 w) Wrk 147 _ _ _ b 4 b (1 v Systlic bld pressure (ram Hg) Rest _+4 ~ Wrk a (5v Wrk 179 _ _+6 ~ _+5 a (300 w) Means + SEM. Cmparisns between results befre and after physical training. ap<0.05; bp<0.01 Cp<0.001 wrk lad. These subjects were therefre excluded frm further analyses. The bld glucse levels were higher in the diabetic than the nn-diabetic subjects (Table 5). Plasma cncentratins f C-peptide as well as f insulin during OGTT were lwer in the diabetic grup. Plasma lipids were nt different. With physical training the plasma C-peptide cncentratins during the glucse tlerance test decreased in the nndiabetic subjects. In cntrast, in the diabetic grup, C-peptide cncentratins increased. Glucse intlerance imprved in the diabetic grup. Insulin r lipid values did nt change in any f the grups. Cmparisns between the diabetic subjects wh were treated with sulfnylurea r nt shwed higher glucse values and lwer C-peptide values in the frmer, but therwise n differences were fund. Bth shwed the same respnse t physical training. Furthermre, n difference in respnse t physical training was seen between men and wmen (nt shwn). Analgus t the nn-diabetic bese subjects in Study I the change in sum f C-peptide values during OGTT crrelated significantly with the C-peptide values befre cmmencing the training prgram as seen in Figure 2. It is als seen that this crrelatin was mainly due t an increase during physical training f lw values, particularly thse which befre training were belw the nrmal range. Here the average values increased dramatically frm 1.93 _ nml/1 befre training t 6.09 _ nml/1 after training (p< 0.001). There were n significant changes in insulin in this subgrup r in the remaining subjects. Euglycaemic glucse clamp studies The results f the euglycaemic glucse clamp studies are shwn in Fig. 3. The glucse dispsal rate was simi- 885 Table 5. Metablic variables f examined grups befre and after physical training (Study li) Cntrl subjects (n = 13) Diabetic subjects (n = 28) Befre After Befre After Fasting glucse _ (mml/l) (p< 0.001) Sum f glucse values during OGT]" a (mml/1) (p < 0.001) Fasting C-peptide _ (nml/l) (p < 0.05) Sum f C-peptide values during OGTF a J a (nml/1) (p< 0.01) Fasting insulin (nml/l) Sum f insulin values during OGTT 2.76 _ _ (nml/1) (t9< 0.01) Triglycerides _ (rnml/1) Chlesterl (mml/l) _+ 0.2 OGTF: Oral glucse tlerance test Means + SEM Cmparisns between cntrl and diabetic subjects (within parentheses) and between results befre and after physical training. a p< 0.05

6 886 M. Krtkiewski et al.: Training in diabetes lar in the diabetic and nn-diabetic grups at bth lw and high insulin infusin rates. Physical training increased the glucse dispsal rate in bth grups, and at bth insulin infusin rates. There was a psitive, significant crrelatin between imprvement in glucse tlerance (sum f glucse values during OGTI" befre - after) and the glucse dispsal rate (per kg LBM) in the glucse clamp studies in the diabetic grup (r: 0.65, p< 0.01). Adipse tissue studies Figure 4 depicts the data f insulin binding t adipcytes. There were n significant differences in insulin binding between the grups, neither befre nr after physical training. There was n change in binding after the training perid. Figure 5 shws the insulin effect n glucse incrpratin int triglycerides befre and after training. Adipcytes frm diabetic patients shwed less incrpratin than frm cntrls befre training (p< 0.05). The nn-diabetic grup shwed n change with training. In the diabetic grup, hwever, the insulin stimulated glucse incrpratin was significantly increased after physical training. Basal and nradrenaline-stimulated liplysis as well as the antiliplytic respnse f insulin, were similar in bth grups, and were nt significantly changed by the training perid. Insulin sensitivity, evaluated as the insulin cncentratin giving half-maximal antiliplytic effect, was als unchanged fllwing the training perid (data nt shwn). -d 4.0 E,,, ~+! 0.0 ~ -4.!, +t ~ SUM OF C-PEPrIDE ( nml/l ) Fig.2. The relatinship between the sum f plasma C-peptide cncentratins during glucse tlerance test befre training and the change in these values with physical training in patients with Type 2 diabetes, y= x; =0.35 ptb <0.01. Shaded area; Mean 2 SD f values fr nn-bese cntrls (Study II) 28-. "T 20- E _J E 12- /,. "T 20- LOW INSULIN INFUSION RATE HIGH INSULIN INFUSION RATE +_T_ --, ~k,._ L L,,/~ Discussin C-peptide and insulin are released frm the B cell in equimlar amunts [14, 15]. In cntrast t insulin, C- peptide is nt taken up by the liver in animals [16, 17] r in man [18, 19]. Measurements f C-peptide cncentratins in peripheral bld therefre give a better estimate f insulin secretin than measurements f peripheral insulin cncentratins. The validity f evaluating insulin secretin by C-peptide cncentratin measurements depends, hwever, n several additinal prerequisites. First, metablic clearance rate (MRC) has t be knwn t allw transfrmatins f cncentratin t actual secretin f insulin and C-peptide. If this is nt knwn, MCR has at least t be cnstant in different cnditins, and cmparable between different grups. MCR f C-peptide des nt change with stimulatin f insulin secretin. Uptake is apparently nt ccurring in muscle and adipse tissue, and the main excretry rute is via the kidneys [20]. Urinary clearance f C-peptide is essentially independent f the plasma C- peptide cncentratin, and similar in nrmal weight, bese and diabetic subjects in relatin t creatinine secretin [21, 22], and MCR f C-peptide is nt different > el Cntrl subjects Diabetic subjects Cntrt subjects Diabetic subjects Fig.3. Glucse dispsal rate in diabetic and cntrl subjects during euglycaemic clamp befre (hatched bars) and after (pen bars) physical training at tw different insulin infusin rates ( and mu/min, respectively). *p<0.05; **p<0.001; ***p< (Means_SEM) n=13 and n=10 fr cntrl and diabetic patients respectively (Study II) between nn-diabetic and diabetic subjects [23]. Taken tgether this infrmatin seems t make it pssible t cnclude that C-peptide secretin frm the B cell is equivalent t insulin secretin, and that liver uptake des nt invalidate estimatin f insulin secretin frm C-peptide determinatins. In summary, this means that the plasma C-peptide cncentratins in the present wrk prbably are useful indices f insulin secretin. The crrelatin between the decrease and initial value f C-peptide (Fig. 1 b) is partly a statistical artefact

7 M. Krtkiewski et al.: Training in diabetes ' 8 % ~ 0.I0 t-1 LI_ 0.05 B/F 0.05].'~, 10 t' IJ_ 0.05 B/F IOlL 0.05 I "~~s tb i I0 I()0 { Ib I()O a Insulin cncentratin b Insulin cncentratin ng/rn[ ng/m[ Fig.4a and b. Specific 125I-insulin binding t adipcytes in a diabetic and b cntrl subjects befre (pen circles) and after (filled circles) physical training. Inserted are shwn the Scatchard plts. Bund insulin expressed as ng/106 cells. (Means _ SEM) n= 12 and n= 17 fr cntrl and diabetic subjects, respectively (Study II) 15" Cntrl subjects Diabetic subjects (~O 0 Insulin cncentratin ~tu/m[ Fig.5. Basal and insulin stimulated UJ4C-glucse incrpratin int triglycerides in diabetic and cntrl subjects befre (hatched bars) and after (pen bars) physical training. * p < (Means + SEM). n=12 and n=18 fr cntrl and diabetic subjects, respectively (Study II) (regressin twards the mean) caused by the randm errrs (measurement errrs and intraindividual variatin). If the standard deviatin f the randm errrs were knwn it wuld be pssible t cmpute t what extent the bserved crrelatin is a bilgical reality. Lacking such precise infrmatin we can investigate whether the bserved crrelatin can pssibly be caused by the randm errrs alne. Such cmputatins shw that with the cefficient f variatin f the randm errrs equal t 10% the (false) crrelatin wuld be 0.03 and with a variatin f 20% the crrelatin wuld be A crrelatin cefficient 0.28 can thus hardly be an effect f regressin twards the mean. The bservatin must, hwever, be cnsidered as a rather weak indicatin f a bilgical relatinship since ne has als t take int accunt the sampling errrs in the crrelatin cefficient. The bserved value differs frm zer nly at the 5% significance level. These cnsideratins thus make it unlikely that the bserved crrelatin was explainable ther than t a minr degree by a statistical artefact. Therefre further analyses were perfrmed with the material f bese subjects divided int grups with nrmal, lw and high C-peptide values using cntrl values as guidance. Hyperinsulinaemia was fund in all the subgrups f besity (Table 3). Hypersecretin f insulin was, hwever, fund nly in the HIS grup, while in the LIS grup the insulin secretin was markedly lw. These findings indicate different causes t the hyperinsulinaemia in besity. One pssible explanatin might be fund in differences in the liver uptake f insulin. If this is the main explanatin the mlar ratis f insulin and C-peptide cncentratins in Table 3 suggest that very little f secreted insulin is taken up in the liver in the LIS grup, while the liver uptake in the NIS and HIS grups wuld be apprximately 60% and 70% respectively (sum f values). These bservatins cnfirm previus reprts [24, 25]. In the ttal grup f bese, nn-diabetic subjects (study I) physical training was fllwed by nly limited changes in the metablic and hrmnal variables. When divided int subgrups accrding t the initial insulin secretin, as indicated by C-peptide cncentratins, it was fund, hwever, that high and nrmal insulin secretrs shwed a decreased secretin after physical training. This was als the case with the bese cntrls in study II, wh were n an average high insulin secretrs with similar C-peptide values as the besity HIS grup in study I. This has been bserved repeatedly befre by measurements f insulin [4, 26, 27] and C- peptide [28]. In bese subjects with lw insulin secretin, hwever, physical training was fllwed by increased C-peptide values. Cnfirming previus studies [4, 28], n changes were seen in glucse tlerance r in bdy cmpsitin variables. Patients with diabetes mellitus imprved their glucse tlerance with physical training. This ccurred

8 888 M. Krtkiewski et al.: Training in diabetes withut changes in bdy cmpsitin and plasma insulin. C-peptide cncentratins increased, hwever. A clser analysis f this phenmenn revealed that this increase was mst prnunced in thse patients wh initially had the lwest C-peptide values, again indicating that physical training in this situatin actually causes an increase f a lw insulin secretin. Taken tgether these data then indicate that in cn- : ditins with insulin hypersecretin, physical training results in a decreased insulin secretin. In cntrast, in subjects with abnrmally lw insulin secretin this is elevated after physical training. Insulin hypersecretin is usually cnsidered t be the result f a cmpensatin fr an increased peripheral insulin resistance. When this resistance is lwered by physical training, as evidenced here by the glucse clamp studies, then cnsequently insulin secretin decreases. It is less clear why insulin secretin increases after physical training in cnditins with lw insulin secretin. It has previusly been shwn that physical training is fllwed by an increased sensitivity in bth the chlinergic [29] and B-adrenergic [30] nervus systems, bth stimulating insulin secretin. It is therefre suggested that this increased sensitivity is the cause t the increased insulin prductin after physical training in cnditins with lw insulin secretin reprted here. The changes in C-peptide cncentratins after physical training were much mre prnunced than thse in insulin. Neither when an elevated C-peptide cncentratin was lwered nr when C-peptide values were increased were insulin cncentratins in the periphery different after training as cmpared with befre. The unchanged peripheral insulin cncentratins in spite f alteratins in insulin secretin indicate that the uptake f insulin in the liver and/r periphery was altered. Insulin clearance did nt differ after as cmpared with befre training as measured with the glucse clamp technique (data nt shwn), indicating that changes in the remval f insulin in the periphery was nt changed by physical training. This in turn suggests that the uptake f insulin in the liver changed. In the case f an increased, lw insulin secretin this then prbably meant that the liver uptake f insulin had increased. This suggestin is supprted by the fact that insulin uptake in the liver is dependent n the prtal cncentratin f insulin [31], in turn dependent n insulin secretin. It seems reasnable t assume that this extra prductin f insulin after physical training, captured by the liver, cntributed t the imprvement f glucse intlerance seen in the diabetic subjects where the initial insulin secretin was subnrmal. Euglycaemic clamp studies The glucse dispsal rate estimated by the euglycaemic clamp shwed n difference between the grups with r withut diabetes mellitus, indicating a similar peripheral insulin effect n glucse uptake in these grups which bth were smewhat bese. The fact that the diabetic grup did nt appear resistant t insulin as cmpared t the nn-diabetic grup des nt mean that they were nrmal with regard t insulin sensitivity and respnsiveness. Rather insulin resistance was prbably equally present in bth grups. This was, hwever, imprved by physical training t a similar extent in bth grups. Frm ther studies it is knwn that insulin sensitivity is increased in muscles during cntractin [32, 33] r after physical training [34], while this des nt seem t be the case in the liver [34]. The effects f physical training seen in the glucse clamp studies were then presumably mainly due t an increase f glucse uptake in muscles [35]. Althugh an increase f peripheral effectiveness f insulin ccurred in bth grups, it was nly in the diabetic subjects that glucse tlerance imprved. The imprvement in glucse tlerance crrelated with the increase in glucse dispsal rate in the clamp measurement in the diabetic grup. Whether these phenmena are causally related remains t be clarified, but this seems at least t be a reasnable pssibility. Adipse tissue studies Adipse tissue nly plays a minr rle fr ttal bdy glucse hmestasis, as cmpared t muscles and liver [36]. Hwever, since insulin sensitivity and respnsiveness in fat cells seem t reflect the severity f glucse intlerance in diabetic subjects [37, 38], it may be f interest t cmpare data btained frm adipcytes in vitr with thse fund with the glucse clamp technique. Therefre, t further elucidate the cellular mechanisms explaining the higher rate f glucse dispsal fllwing physical training, studies n abdminal fat cells were perfrmed. Insulin binding has been fund nt t deviate frm nrmal in fat cells frm bese and Type 2 diabetic patients [37, 38]. The present study cnfirms these results. Furthermre, insulin binding was nt changed fllwing physical training in accrdance with previus reprts [39, 40]. In mncytes an increased binding has been fund [41, 42], but these cells are nt natural target cells fr insulin and, therefre, such data are less readily interpreted. Increased insulin binding t fat cells has been reprted after physical training in rats [43]. A recent study seems t reslve this cntrversy shwing that the increase in insulin binding, when fund after physical training, is f such small magnitude that it has n bvius physilgical significance in cmparisn with the increase in glucse transprt [44]. Differences in insulin binding are reflected by a shift f the dse-respnse curve fr insulin (altered insulin sensitivity) whereas a change in the maximal insulin effect (insulin respnsiveness) mirrrs pstreceptr defect(s) [45]. Accrdingly, insulin binding and insulin sensitivity, measured as the antiliplytic effect, were nt changed in this study. In cntrast, insulin respnsive-

9 M. Krtkiewski et al.: Training in diabetes 889 ness, as indicated by the maximal glucse incrpratin int triglycerides, was significantly imprved after physical training in the diabetic patients. Increased glucse transprt capacity has been fund previusly in fat cells frm trained rats [44]. The glucse clamp data indicate that physical training results in an increased insulin respnsiveness, because glucse dispsal rate was increased bth at the lw (submaximal) and the high (maximal) insulin infusin rates. Adipse tissue data then als shw that the effect f training n the insulin respnsiveness f glucse metablism is due t pstreceptr changes, and with n changes in insulin binding. These parallel findings suggest that, fllwing physical training, similar reactins are ccurring in ther tissues where glucse uptake is quantitatively mre significant than in adipse tissue. The insulin resistance in fat cells frm Type 2 diabetic subjects is mainly due t a diminished insulin respnsiveness f glucse metablism, prbably due t a pstreceptr-defect f glucse transprt [37, 38]. Hence, it is suggested that when physical training causes a reversal f this pstreceptr defect, an imprvement in glucse tlerance is btained. In cnclusin, this study has shwn that an imprvement f glucse tlerance is btained when mderately bese, diabetic subjects have been trained physically. Previus studies [1, 2] and studies appearing while this wrk was in prgress [47-49] have shwn varying results, which may be due t the fact that different subgrups f Type 2 diabetic patients react differently t physical training. The effect is prbably partly due t an increase f the insulin effectiveness n peripheral glucse uptake, presumably f main quantitative imprtance in muscles. This imprvement is accentuated by an increase f lw insulin secretin, prbably resulting in better insulinizatin f the liver. Taken tgether this then indicates that physical training imprves glucse tlerance by increasing insulin effects bth in the peripheral tissues (by increased tissue respnsiveness, due t a reversal f a pstreceptr defect), and in the liver (by uptake f an increased insulin secretin). Finally, it shuld be emphasized that the present study has shwn an imprvement f glucse tlerance by physical training in the absence f bdy cmpsitin changes. When bdy fat decreases in physical training prgrams, the effects n glucse tlerance and glucse hmestasis are prbably mre prnunced [46]. Acknwledgements. The statistical advice f N. Blmqvist, Ph.D., Department f Statistics, University f Grtebrg is gratefully acknwledged. This study was supprted by the Swedish Medical Research Cuncil (prject n. B 85-19X ), Nrdic Fundatin fr Research withut Animals, Greta and Einar Asker's Fundatin and Hjalmar Svenssn's Fundatin. References 1. Ruderman NB, Ganda OP, Jhansen K (1979) The effect f physical training n glucse tlerance and plasma lipids in maturity-nset diabetes. Diabetes 28 (Suppl 1): Saltin B, Lindg~irde F, Hustn M, Hrlin R, Nygaard E, Gad P (1979) Physical training and glucse tlerance in middle-aged men with chemical diabetes. Diabetes 28 (Suppl 1) Cstill DL, Cleary P, Fink WJ, Fster G, Ivy JL, Witzmann F (1979) Training adaptatins in skeletal muscle f juvenile diabetics. Diabetes 28: Bj6rntrp P, de Junge K, SjrstrOm L, Sullivan L (1970) The effect f physical training n insulin prductin in besity. Metablism 19: Natinal diabetes data grup. Natinal Institute f Health, Bethesda Maryland USA (1979) Classificatin and diagnse f diabetes mellitus and ther categries f glucse intlerance. Diabetes 2: SkrldbrnH, ArvidssnB, AnderssnM (1972) A new whle bdy mnitring labratry. Acta Radil 313 (Suppl): Frbes GB, Gallup J, Hurch JB (1961) Estimatin f ttal bdy fat frm ptassium-40 cntent. Science 133: SjrstrOm L, Bjrrntrp P, Vrana J (1971) Micrscpic fat cells size measurements n frzen-cut adipse tissue in cmparisn with autmatic determinatins f smium-fixed fat cells. J Lipid Res 12: ,~strand I (1960) Aerbic wrk capacity in men and wmen with special reference t age. Acta Physil Scand 49 (Suppl) Smith U, Sjrstr6m L, Bj6mtrp P (1972) Cmparisn f tw methds t determine human adipse cell size. J Lipid Res 13: GammeltftS, GliemannJ (1973) Binding and degradatin f 125-I-insulin by islated rat fat cells. Bichem Biphys Acta 320: Laurell S, Tibblin G (1966) An enzymatic flurimetric micrmethd fr the determinatin f glycerl. Clin Chim Acta 13: Dle VP, Meinerts H (1960) Micrdeterminatin f lng-chain fatty acids in plasma and tissue. J Bil Chem 235: Heding LG, Larsen OD, Markussen J, Jrgensen KH, Hallund O (1974) Radiimmunassays fr human, prk and f C-peptide and related substances. Hrm Metab Res 5 (Suppl): Hrwitz DL, Starr JI, Mak ME, BlackardWE, RubensteinAH (1975) Prinsulin, insulin and C-peptide cncentratins in human prtal and peripheral bld. J Clin Invest 55: Stll RW, TuberJL, Menahan LA, Williams RH (1970) Clearance f prcine insulin, prinsulin and cnnecting peptide by the islated rat liver. Prc Sc Exp Bil Med 111: Katz AI, Rubenstein AH (1973) Metablism f prinsulin, insulin and C-peptide in the rat. J Clin Invest 52: Canivet B, Krebs BP (1980) C-peptide uptake and excretin by the liver in man. Hrm Metab Res 12: Bratusch-Marain PR, Waldh~iusl WK, Gasic S, Hfer A (1984) Hepatic dispsal f bisynthetic human insulin and prcine C-peptide in humans. Metablism 33: Fiber OK, Kehlet H, Madsbad S, Binder C (1978) Kinetics f human C-peptide in man. Diabetes 27 (Suppl 1): Blix PM, Bddie-Willis C, Landau RL, Rchman H, Rubenstein AH (1982) Urinary C-peptide; an indicatr f beta-cell secretin under different metablic cnditins. J Clin Endcrinl Metab 54: Meistas MT, Rendell M, Marglis S, Kwarski AA (1982) Estimatin f the secretin rate f insulin frm the urinary excretin rate f C-peptide. Study in bese and diabetic subjects. Diabetes 31 : Faber OK, Hagen C, Binder C, Markussen J, Naithani VK, Blix PM, Kuzuya H, Hrwitz DL, Rubenstein AH, Rssing N (1978) Kinetics f human cnnecting peptide in nrmal and diabetic subjects. J Clin Invest 62: Rssell R, Gmis R, Casamitjana R, Segura E, Vilardell E, Rivera F (1983) Reduced hepatic insulin extractin in besity: relatinship with plasma insulin levels. J Clin Endcrinl Metab 56: Malmquist J, Lindg~irde F, Nrdrn G (1981) Plasma insulin and C-peptide in nrmal and glucse intlerant males: the rle f hepatic insulin uptake. Acta Med Scand 656: Bj6mtrp P, Fahlrn M, Grimby G, Gustafsn A, Hlm J, Renstrrm P, Scherst~n T (1972) Carbhydrate and lipid metab-

10 890 M. Krtkiewski et al.: Training in diabetes lism in middle-aged physically well-trained men. Metablism 1: Lhmann D, Liebld F, Heilmann W, Stenger J, Phl A (1978) Diminished insulin respnse in highly trained athletes. Metablism 27: Krtkiewski M, Bjtrntrp P, Hlm G, Marks V, Mrgan L, Smith U, Feurle GE (1984) Effects f physical training n insulin, cnnecting (c-peptide) gastric inhibitry plypeptide (GIP) and pancreatic plypeptide (PP) levels in bese subjects. Int J Obesity 8: Krtkiewski M, Sjtstrtm L, Bjtrntrp P (1980) Physical training in hyperplastic besity. V. Effects f atrpine n plasma insulin. Int J Obesity 4: Krtkiewski M, Mandrukas K, Mrgan L, William-Olssn T, Feurle GE, yn Schenk M, Bjtmtrp P, Sjtstrtm L, Smith U (1983) The effects f physical training n adrenergic sensitivity in besity. J Appl Physil 55: Karakash C, Assimacpuls-Jeannet F, Jeanrenaud B (1976) An anmaly f insulin remval in perfused livers f bese-hyperglycemic. (b/b) mice. J Clin Invest 57: Hllszy JO, Narahara HT (1965) Studies n tissue permeability X. Changes in permeability t 3-methylglucse assciated with cntractin f islated frg muscle. J Bil Chem 240: Berger M, Hagg S, Ruderman NB (1975) Glucse metablism in perfused skeletal muscle. Bichem J 146: MndnCE, Dlkas CB, Reaven GM (1980) Site f enchanged insulin sensitivity in exercise-trained rats at rest. Am J Physi1239: E169-E De Frnz RA, Tbin JD, Andres R (1979) Glucse clamp technique; a methd fr quantifying insulin secretin and resistance. Am J Physi1237:E214-E Bjtrntrp P, Berchtld P, Hlm J, LarssnB (1971) The glucse uptake f human adipse tissue in besity. Eur J Clin Invest 1 : Ltnnrth P, DiGirlam M, Krtkiewski M, Smith U (1983) Insulin binding and respnsiveness in fat cells frm patients with reduced glucse tlerance and type II diabetes. Diabetes 32: Kashiwagi A, Vers MA, Andrews J, Vasques B, Reaven G, Fley JE (1983) In vitr insulin resistance f human adipcytes islated frm subjects with nninsulin-dependent diabetes mellitus. J Clin Invest 72: Wirth A, Hlm G, Nilssn B, Smith U, Bjtrntrp P (1980) Insulin kinetics and insulin binding t adipcytes in physically trained and fdrestricted rats. Am J Physil 238:E105-E Wardzala L, Hrtn E, Jeanrenaud B (1980) Physical training increases glucse transprt and metablism in rat adipse cells withut altering insulin binding r sensitivity. Alim Nutr Metab 1 : 376 (Abstract) 41. Sman V, Kivist V, Diebert D, Felig P, de Frnz R (1979) Increased insulin sensitivity and insulin binding t mncytes after physical training. N Engl J Med 301: Kivist V, Sman V, Cnrad P, Hendler R, Nadel E, Felig P (1979) Insulin binding t mncytes in trained athletes. J Clin Invest 64: Craig BW, Hammns GT, Gartwaite SM, Jarett J, Hllszy JO (1981) Adaptatins f fat cells t exercise: respnse t glucse uptake and xidatin t insulin. J Appl Physil 51: Vinten H, Galb H (1983) Effect f physical training n transprt and metablism f glucse in adipcytes. Am J Physil E Kahn CR (1978) Insulin resistance, insulin intensitivity and insulin unrespnsiveness; a necessary distinctin. Metablism 27 (Suppl 2): BjOrntrp P, Berchtld P, Grimby G, Lindhlm B, Sanne H, Tibblin G, Wilhelmsen L (1972) Effects f physical training n glucse tlerance, plasma insulin and lipids and n bdy cmpsitin in men after mycardial infarctin. Acta Med Scand 192: Schneider SH, AmrsaLF. Khachadurian AK, Ruderman NB (1984) Studies n the mechanism f imprved glucse cntrl during regular exercise in Type 2 (nn-insulin-dependent) diabetes. Diabetlgia 26: Reitman JS, Vasquez B, Klimes I, Nagulesparan (1984) Imprvement f glucse hmestasis after exercise training in nn-insulindependent diabetes. Diabetes Care 7: Trvati M, Carla Q, Cavart F, Vitari S, Bnandi C, Lucchina PG, Ficchi F, Emanuelli G, Lenti G (1984) Influence f physical training n bld glucse cntrl, glucse tlerance, insulin secretin and insulin actin in nn-insulin-dependent diabetic patients. Diabetes Care 7: Received: 9 Octber 1984 and in revised frm: 30 September 1985 Dr. Per Bj6rntrp Department f Medicine I Sahlgrenska Sjukhuset S Gttebrg Sweden