Research Article Cholesterol Metabolism and Weight Reduction in Subjects with Mild Obstructive Sleep Apnoea: A Randomised, Controlled Study

Transcription

1 Cholesterol Volume 2013, Article ID , 9 pges Reserch Article Cholesterol Metbolism nd Weight Reduction in Subjects with Mild Obstructive Sleep Apnoe: A Rndomised, Controlled Study Mrit Hllikinen, 1 Henri Tuomilehto, 2,3 Trj Mrtikinen, 4 Esko Vnninen, 5 Juh Seppä, 2 Jouko Kokkrinen, 6 Jukk Rndell, 6 nd Helen Gylling 1,7 1 Institute of Public Helth nd Clinicl Nutrition, Deprtment of Clinicl Nutrition, University of Estern Finlnd, P.O. BOX 1627, Kuopio, Finlnd 2 Institute of Clinicl Medicine, Deprtment of Otorhinolryngology, Kuopio University Hospitl, nd University of Estern Finlnd, P.O. BOX 1777, Kuopio, Finlnd 3 Oivuni Sleep Clinic, Puijonktu 12 b, Kuopio, Finlnd 4 Institute of Clinicl Medicine, Deprtment of Medicine, Division of Clinicl Nutrition, Kuopio University Hospitl, P.O.BOX1777,70211Kuopio,Finlnd 5 Institute of Clinicl Medicine, Clinicl Physiology nd Nucler Medicine, Kuopio University Hospitl, nd University of Estern Finlnd, P.O. BOX 1777, Kuopio, Finlnd 6 Institute of Clinicl Medicine, Respirtory Medicine, Kuopio University Hospitl, nd University of Estern Finlnd, P.O.BOX1777,70211Kuopio,Finlnd 7 Division of Internl Medicine, Deprtment of Medicine, University of Helsinki, Helsinki, P.O. BOX 700, HUS, Finlnd Correspondence should be ddressed to Mrit Hllikinen; mrit.hllikinen@uef.fi Received 12 Mrch 2013; Accepted 29 April 2013 Acdemic Editor: Frncisco Blnco-Vc Copyright 2013 Mrit Hllikinen et l. This is n open ccess rticle distributed under the Cretive Commons Attribution License, which permits unrestricted use, distribution, nd reproduction in ny medium, provided the originl work is properly cited. To evlute whether prmeters of obstructive sleep pnoe (OSA) ssocite with cholesterol metbolism before nd fter weight reduction, 42 middle-ged overweight subjects with mild OSA were rndomised to intensive lifestyle intervention (N =23)orto control group (N =18) with routine lifestyle counselling only. Cholesterol metbolism ws evluted with serum noncholesterol sterol rtios to cholesterol, surrogte mrkers of cholesterol bsorption (cholestnol nd plnt sterols) nd synthesis (cholestenol, desmosterol, nd lthosterol) t bseline nd fter 1-yer intervention. At bseline, rteril oxygen sturtion (S O2 ) ws ssocited with serum cmpesterol (P < 0.05) nd inversely with desmosterol rtios (P < 0.001) independently of gender, BMI, nd homeostsis model ssessment index of insulin resistnce (HOMA-IR). Apnoe-hypopnoe index (AHI) ws not ssocited with cholesterol metbolism. Weight reduction significntly incresed S O2 nd serum cholestnol nd decresed AHI nd serum cholestenol rtios. In the groups combined, the chnges in AHI were inversely ssocited with chnges of cholestnol nd positively with cholestenol rtios independent of gender nd the chnges of BMI nd HOMA-IR (P < 0.05). In conclusion, mild OSA seemed to be ssocited with cholesterol metbolism independent of BMI nd HOMA-IR. Weight reduction incresed the mrkers of cholesterol bsorption nd decresed those of cholesterol synthesis in the overweight subjects with mild OSA. 1. Introduction Obstructive sleep pnoe (OSA) chrcterized by repeted episodes of pnoe nd hypopnoe during sleep is one of the most common sleep disturbnces [1]. OSA is independently ssocited with hypertension, crdiovsculr diseses, metbolic syndrome, insulin resistnce, nd type 2 dibetes [2 7]. Furthermore, recent epidemiologicl studies hve concluded tht OSA is n importnt risk fctor for mortlity, prticulrlyduetocoronryrterydisese[8, 9]. However, the underlying mechnisms explining these ssocitions re rther complex, nd lthough severl possibilities hve been proposed, they re not entirely ccepted. In generl, therogenesis s well s OSA is considered s slow processes, ndtheonsetislikelytobeginyersbeforenysymptoms pper.wehveerlierdemonstrtedthtevenmildosais

2 2 Cholesterol ssocited with the ctivtion of the proinflmmtory system [10]. Furthermore, since elevted LDL cholesterol level is one of the most importnt risk fctors for crdiovsculr diseses, the question rises whether OSA hs role in hypercholesterolemi or in cholesterol metbolism. In some, but not in ll studies, OSA hs independently ssocited with incresed concentrtions of totl cholesterol nd triglycerides nd decresed concentrtions of HDL cholesterol [11 14]. The mechnisms of dyslipidemi in OSA besides obesity re not clerly understood especilly for elevted LDL cholesterol level [15],but most likely chronic intermittent hypoxemi (IH), mjor component of OSA, my be the primry trigger for cscde of pthogenetic mechnisms leding to incresed triglyceride-rich lipoproteins nd reduced HDL cholesterol levels [15]. Regrding cholesterol metbolism there re no clinicl studies exmining the ssocition between OSA nd cholesterol metbolism (i.e., cholesterol synthesis nd bsorption). The most importnt risk fctor for OSA is obesity [16]. On the other side, obesity interferes with cholesterol metbolism, so tht cholesterol synthesis is upregulted, nd cholesterol bsorption efficiency is low [17, 18]. Accordingly, it could be ssumed tht cholesterol metbolism might be disturbed in OSA, but whether it is obesity or OSA tht interferes with cholesterol metbolism remins to be evluted. However, this does not chnge the fct tht 60 90% of ll ptients with OSA re obese [19] nd need to be treted not only for OSA but lso other obesity relted comorbidities. It ws recently demonstrted tht lifestyle intervention with weight reduction reduced both hypopnoe nd especilly pnoe indices nd lso other obesity relted risk fctors for crdiovsculr diseses in vst mjority of ptients with mild OSA, highlighting the importnce of n erly lifestyle intervention [20]. Similrly, weight reduction decreses cholesterol synthesis nd increses cholesterol bsorption in type 2 dibetics [21, 22]. It would be interesting to know whether in subjects with OSA weight reduction lters lso cholesterol metbolism, nd whether thereductioninpnoendhypopnoeindicesrerelted to cholesterol metbolism beyond obesity. Therefore, in the present rndomised interventionl study two min prmeters of OSA, tht is, pnoe-hypopnoe index (AHI) nd rteril oxygen sturtion (S O2 ), were relted to those of cholesterol synthesis nd bsorption t bseline nd fter oneyer weight reduction progrm in middle-ged overweight subjects with mild OSA. Cholesterol metbolism ws evluted with serum noncholesterol sterols, surrogte mrkers of cholesterol bsorption nd synthesis [23]. 2. Methods This study is substudy of our rndomised study originlly conducted to determine the effects of chnges in lifestyle with weight reduction progrm designed to prevent the progressionofthediseseorevencureitinthemostprevlent subgroup of OSA, tht is, overweight ptients with mild OSA. The detiled design of the study ws previously reported [20] Subjects. The subjects were consecutively recruited from mong ptients referred to the outptient clinics of Otorhinolryngology nd Respirtory Medicine of Kuopio University Hospitl, Finlnd, becuse of suspicion of OSA. The min study popultion consisted of 72 subjects who completed the 1-yer follow-up [20]. The inclusion criteri were ge yers, overweight (BMI 28 kg/m 2 ), nd mild OSA (AHI 5 15 events/h). The exclusion criteri were ctive tretment of OSA of ny kind, pregnncy, chronic kidney, thyroid, or liver disese. To the present study, n dditionl inclusion criterion ws the vilbility of both bseline nd follow-up mesurements, nd n dditionl exclusion criterion ws the presence of lipid-lowering mediction. This study ws conducted ccording to the guidelines lid down in the Declrtion of Helsinki, nd ll procedures involving humn subjects were pproved by the Reserch Ethics Committee of the Hospitl District of Northern Svo (Kuopio, Finlnd). All subjects gve their written informed consent for the study Intervention. A detiled description of the intervention procedure ws previously reported by Tuomilehto et l. [20]. The subjects with mild OSA were rndomised to two groups. The subjects in the intervention group were provided with group-bsed very low clorie diet (VLCD) of kcl/d for 12 weeks, fter which they were dvised regrding diet ndexercise.thelifestyleinterventionlstedfor1yernd consisted of 14 visits with the study nutritionist. The subjects in the control group were given stndrd cre consisting of generl orl nd written informtion bout diet nd exercisetbselinend3-monthvisitsbythestudynursend physicin without ny specific individulised dvice Mesurements. Nocturnl crdiorespirtory monitoring byemblett(embl,broomfield,co,usa)thomews conducted in ccordnce with ccepted guidelines for dignosing OSA [24]. Apnoe ws defined s cesstion (>90%) of irflow for >10 s with oxygen desturtion for 4%. Hypopnoe ws defined s reduction (>30%) of irflow for >10 s with oxygen desturtion for 4%. AHI ws defined s the number of pnoes nd hypopnoes per hour, nd mild OSA ws defined s n AHI of 5 15 events/h [24]. Furthermore, men rteril oxygen sturtion (S O2 )nd time nd percentge with rteril oxygen sturtion <90% were ssessed. The recordings were mnully evluted by two blinded, trined physicins. Body weight ws mesured with digitl scle nd height using stdiometer. A trined nurse mesured lso wist circumference both t the bseline nd t the 1-yer visit. Blood smples for biochemicl ssys were collected from fsting subjects ( 12 h). Serum totl nd HDL cholesterol, serum triglycerides nd plsm glucose were nlysed by using utomted nlyzer system (Konelb 60 Anlyzer, ThermoFisher Scientific, Wlthm, MA, USA). LDL cholesterol ws clculted ccording to Friedewld eqution. Plsm glucose ws nlysed by using utomted nlyzer system (Konelb 60 Anlyzer, ThermoFisher Scientific, Wlthm, MA, USA). Serum insulin ws mesured by

3 Cholesterol 3 using fluoroimmunossy system (Wllc, Perkin-Elmer, Wlthm, MA, USA). The homeostsis model ssessment index of insulin resistnce (HOMA-IR) ws clculted s fsting serum insulin concentrtion fsting plsm glucose concentrtion/22.5 [25]. Serum cholesterol, cholesterol precursors reflecting cholesterol synthesis (squlene, cholestenol, lthosterol, nd desmosterol), plnt sterols (sitosterol nd cmpesterol), nd cholestnol reflecting cholesterol bsorption [23]were quntified from nonsponifible serum mteril by GLC (Agilent 7890GC System, Agilent Technologies, Wilmington, DE, USA) equipped with 50 m long Ultr 1 cpillry column (5% Phenyl-methyl siloxne) (Agilent Technologies, Wilmington, DE, USA) [26]. Serum vlues were expressed in terms of 10 2 x mmol/mol of cholesterol (clled rtio in the text) by dividing the noncholesterol sterol concentrtions with the cholesterolvlueofthesmeglcruntoelimintethe chnging concentrtions of lipoproteins (minly LDL) tht trnsports noncholesterol sterols. Rtios of reltive synthesis mrkers/bsorption mrkers were lso clculted reflecting cholesterol metbolism Sttisticl Anlyses. Sttisticl nlyses were performed with SPSS for Windows 14.0 sttistics progrm (SPSS, Chicgo, IL, USA). Normlity nd homogeneity of vrince ssumptions were checked before further nlyses. Student s t-test ws used to compre the bseline vlues nd the chnges between the groups. ANOVA for repeted mesurements ws used to nlyse the interction of time nd group nd chnges over time in between-group comprisons followed by post hoc comprisons with Bonferroni corrections. In between-group comprisons, gender nd BMI, were included s ANCOVA. For some vribles of interest Person or Spermn correltion coefficients were clculted. In ddition, to evlute the effects of gender, BMI nd HOMA-IR on ssocitions of prmeters of OSA nd cholesterol metbolism, multiple liner regression nlysis ws used. Vribles not normlly distributed even fter logrithmic trnsformtion, nonhomogenous in vrince, or noncontinuous were tested with Mnn-Whitney U test or Fisher exct test. A P vlue of <0.05 ws considered sttisticlly significnt. The results re given s mens ± SEM. 3. Results 3.1. Bseline. Atotlof41subjects(33mennd8women) fulfilled the criteri nd were included into the sttisticl nlyses. Their men ge ws 48.9 ± 1.3 yers nd BMI 32.5 ± 0.4 kg/m 2. Thirteen subjects hd ntihypertensive mediction, two hd thyroxin therpy, nd one hd orl dibetes mediction. Bseline chrcteristics of the subjects in the control (N = 18)ndintervention(N = 23) groups re shown in Tble 1. Despite rndomistion, the subjects in the intervention group were hevier, nd their BMI ws higher nd wist circumference lrger thn in the control group. In ddition, serum insulin concentrtion nd cholestenol : cholesterol rtio were greter, nd HOMA-IR tended to be significntly greter (P = 0.055)compred with controls (Tble 2). No other significnt differences between the groups were observed Bseline Associtions. In the whole popultion, cholesterol synthesis mrkers were interrelted (e.g., cholestenol versus lthosterol r = 0.572, P < 0.001)swellsthebsorption mrkers (cmpesterol versus cholestnol r = 0.664, P < 0.001). Cholesterol synthesis mrkers were inversely ssocited with the bsorption mrkers (e.g., desmosterol versus cholestnol r = 0.637, P < 0.001) suggestingtht cholesterol homeostsis ws intct. The mrkers of cholesterol synthesis were positively (e.g., desmosterol rtio r = 0.364, P = 0.020) ndthoseof cholesterol bsorption inversely (e.g., cholestnol rtio r = 0.376, P = 0.020) ssocited with BMI. The cholesterol synthesis mrkers were inversely ssocited with serum HDL cholesterol concentrtion (e.g., desmosterol rtio r = 0.502, P = 0.001) nd positively with serum triglycerides (e.g., desmosterol rtio r = 0.546, P < 0.001), wheres thessocitionsbetweenthebsorptionmrkersndhdl cholesterol (e.g., cholestnol rtio r = 0.316, P = 0.040) nd triglycerides (e.g., cholestnol rtio r = 0.343, P = 0.028) were opposite. No ssocitions of the cholesterol synthesis nd bsorption mrkers with totl nd LDL cholesterol were found. Men totl AHI ws not ssocited with men rteril oxygen sturtion (S O2 )orwithnyothervribles,even though AHI tended to be ssocited with serum cholestenol rtiotocholesterol(r = 0.292, P = 0.064). S O2 ws inversely ssocited with body weight (r = 0.656, P < 0.001) nd wist circumference (r = 0.481, P= 0.003) nd positively with HDL cholesterol concentrtion (r = 0.410, P = 0.010). S O2 ws inversely ssocited with desmosterol (r = 0.595, P < 0.001) ndposi- tively with cmpesterol rtios to cholesterol (r = 0.381, P = 0.020). In multiple liner regression nlysis fter djustment with gender, BMI nd HOMA-IR, the ssocitions between S O2 nd desmosterol nd cmpesterol rtios to cholesterol nd desmosterol : cmpesterol rtio remined significnt (Tble 3) Intervention Anthropometric Mesurements. BMI nd wist circumference reduced significntly more in the intervention group compred with the control group ( 13.6% versus 2.2% nd 10.9% versus 2.2%, resp.) (Tble 1)duringthefollow-up Serum Cholesterol, Plsm Glucose, nd Serum Insulin. Plsm glucose ws similrly reduced in both study groups (P < 0.05),butthereductionwsnotsignificntfter djustment with gender nd BMI (Tble 1). The reduction in serum insulin concentrtion ws greter in the intervention group compred with the controls ( 43.6% versus 17.8%, P < 0.05), but the intervention vlues did not differ between the groups (Tble 1).Similrly,the percentge reduction in

4 4 Cholesterol Tble 1: Chnges in nthropometric mesurements, plsm glucose nd serum insulin concentrtions, nd crdiorespirtory vribles during the intervention. Control group Intervention group Bseline 12 months Bseline 12 months Gender (M/F) 14/4 19/ Age (y) 48.2 ± ± Weight (kg) 93.9 ± ± ± 2.2 c 91.5 ± 2.4 d,e <0.001 <0.001 BMI (kg/m 2 ) 31.4± ± ± 0.6 c 29.5 ± 0.6 d,e <0.001 <0.001 Wist circumference (cm) ± ± ± 2.1 c ± 2.0 d,e <0.001 <0.001 P-Glucose (mmol/l) (f) 6.19 ± ± ± ± S-Insulin (mu/l) ± ± ± 1.69 c 7.16 ± HOMA-IR 2.66± ± ± ± Totl cholesterol (mmol/l) 5.17 ± ± ± ± LDL cholesterol (mmol/l) 3.13 ± ± ± ± HDL cholesterol (mmol/l) 1.13 ± ± ± ± 0.06 d Totl triglycerides (mmol/l) (f) 1.78 ± ± ± ± AHI (totl) 9.5 ± ± ± ± 1.2 d,(e) Men S O ± ± 0.3 d 94.0 ± ± 0.3 d,e < Time with S O2 < 90% 3.5 ± ± ± ± 2.1 d,e Percentge time with S O2 < 90% 0.9 ± ± 0.9 d 1.6 ± ± 0.3 d,e Vlues shown re mens ± SEM. Group by time interction nlysed with nlysis of vrince for repeted mesurements (GLM). If the bseline differed between groups (P < 0.06), it ws tken into ccount s covrince. (Gender Fisher s exct test nd ge Student s t-test). b Group by time interction (gender nd BMI s covrince). c P < 0.05 denotes significnt difference t the bseline between the groups. d P < 0.05 denotes significnt difference from the bseline within the groups. e P < 0.05 denotes significnt difference t the 12 months between the groups, (e) P > 0.05 (genderndbmiscovrince). f P < 0.05 denotes significnt chnge over time, (f) P > 0.05 (genderndbmiscovrince). P P b HOMA-IR ws greter in the intervention group compred with the controls ( 46.7% versus 19.5%, P < 0.05). group spent less time with S O2 < 90% during their sleep compred with subjects in the control group (Tble 1) Serum Lipids. Serum totl nd LDL cholesterol concentrtions were not chnged during the intervention (Tble 1). Serum HDL cholesterol concentrtion significntly incresed in the intervention group, nd the percentge increse ws greter thn in the control group. However, the intervention vlues did not differ between the groups (Tble 1). Serum triglyceride concentrtion ws similrly reducedinbothstudygroups(p < 0.05), but the reductions were not significnt fter djustment with gender nd BMI (Tble 1) Crdiorespirtory Recordings. The men totl AHI t 12 months nd the men percentge chnge ( 49.1% versus +30.9%) during the follow-up significntly differed between the groups (Tble 1). However, fter djustment with gender ndbmithementotlahionlytendedtobelowerinthe intervention group compred with controls (P = 0.052). A significnt improvement ws detected in men S O2 in the intervention group compred with the control group t 12 months (Tble 1). In ddition, the subjects in the intervention Cholesterol Synthesis nd Absorption Mrkers. Of the cholesterol synthesis mrkers, serum cholestenol rtio to cholesterol ws significntly reduced by 18.1% in the intervention group, nd the chnge ws significntly different compred with the controls (Tble 2). Serum desmosterol ndlthosterolrtiostocholesterolsimilrlyreducedinboth groups (P < 0.05), but the reductions were not significnt fter djustment with gender nd BMI (Tble 2). No chnges in serum squlene were found (Tble 2). Of the cholesterol bsorption mrkers, serum cholestnol : cholesterol rtio significntly incresed by 11.4% during the follow-up in the intervention group, nd the chnge ws significntly different compred with the controls (Tble 2). However, the intervention vlues did not differ between the groups (Tble 2). Serum cmpesterol nd sitosterol rtios to cholesterol did not chnge (Tble 2). The chnges in the concentrtions of serum cholesterol synthesis nd bsorption mrkers were in line with the respective chnges in the rtio to cholesterol (dt not shown).

5 Cholesterol 5 Tble 2: Chnges in serum noncholesterol sterols nd squlene during the intervention. Control group Intervention group Bseline 12 months Bseline 12 months Cholesterol (mg/dl) ± ± ± ± Cholesterol synthesis mrkers Squlene : cholesterol 26.5 ± ± ± ± Cholestenol : cholesterol 15.2 ± ± ± 2.9 c 18.0 ± 2.9 d,e Desmosterol : cholesterol (f) 66.3 ± ± ± ± Lthosterol : cholesterol (f) ± ± ± ± Cholesterol bsorption mrkers Cmpesterol : cholesterol ± ± ± ± Sitosterol : cholesterol ± ± ± ± Cholestnol : cholesterol ± ± ± ± 6.7 d Cholesterol metbolism mrkers Squlene : Cholestnol 0.21 ± ± ± ± Cholestenol : Cholestnol 0.12 ± ± ± 0.03 c 0.14 ± 0.02 d,e Desmosterol : Cholestnol 0.54 ± ± ± ± 0.04 d Lthosterol : Cholestnol 1.42 ± ± ± ± 0.17 d Vlues shown re mens ± SEM. Group by time interction nlysed with nlysis of vrince for repeted mesurements (GLM). If the bseline differed between groups (P < 0.05), it ws tken into ccount s covrince. b Group by time interction (gender nd BMI s covrince). c P < 0.05 denotes significnt difference t the bseline between the groups. d P < 0.05 denotes significnt difference from the bseline within the groups. e P < 0.05 denotes significnt difference t the 12 months between the groups. f P < 0.05 denotes significnt chnge over time (f) P > 0.05 (genderndbmiscovrince). P P b Tble 3: Associtions between serum desmosterol nd cmpesterol rtios to cholesterol nd desmosterol : cmpesterol rtio nd S O2. Desmosterol : cholesterol Cmpesterol : cholesterol Desmosterol : cmpesterol Bet P vlue Bet P vlue Bet P vlue Gender BMI (kg/m 2 ) HOMA-IR < S O R Multiple liner regression nlysis models (djustment with gender, BMI, nd HOMA-IR). Serum cholestenol, desmosterol, nd lthosterol rtios to cholestnol significntly reduced by % during the follow-up in the intervention group, nd the chnges significntly differed from controls, but only the intervention vlues of cholestenol : cholestnol rtio significntly differed compred with controls (Tble 2) Associtions during Intervention (Intervention + Control Groups Combined). Figure 1 shows the percentge chnges in AHI, S O2, cholestenol, nd cholestnol : cholesterol rtios in reltion to weight reduction. The greter the weight reduction, the greter the reductions in AHI nd serum cholestenol : cholesterol rtio nd the increses in S O2 nd serum cholestnol : cholesterol rtio. The percentge chnge of AHI ws positively ssocited with the respective chnges of serum synthesis mrkers (e.g., serum cholestenol : cholesterol rtio, Figure 2()) nd inversely with the percentge chnge of serum cholestnol : cholesterol rtio (Figure 2(b)). After djustment with gender nd the percentge chnges of BMI nd HOMA- IR, the ssocitions between the percentge chnges of AHI nd cholestnol : cholesterol rtio (P = 0.004) nd of the cholesterol synthesis mrkers cholestenol : cholesterol (P = 0.021) remined significnt. The positive ssocitions between the percentge chnges of AHI nd cholestenol, desmosterol, nd lthosterol rtios to cholestnol (r = , P = ) remined significnt fter djustment with gender nd the percentge chnges of BMI nd HOMA-IR, too. However, the inverse ssocitions

6 6 Cholesterol Chnge (%) < to 5 5 to 0 >0 Weight chnge from bseline to 12 month follow-up (kg) AHI S O2 Cholestenol Cholestnol Figure 1: The percentge chnges in pnoe-hypopnoe index (AHI), men oxygen sturtion (S O2 ), nd cholestenol nd cholestnol : cholesterol rtios (10 2 x mmol/mol of cholesterol) in reltion to chnges in body weight: less thn 10 kg, 10 to 5kg,nd 5 to 0 kg nd more thn 0 kg P < 0.05 or less from weight reduction of < 10 kg, b P < 0.05 or less from weight reduction of 5to0kg. between the percentge chnges of S O2 nd cholestenol nd desmosterol rtios to cmpesterol (r = , P = ) did not remin significnt fter djustment with gender nd the percentge chnges of BMI nd HOMA-IR. 4. Discussion The novel observtions of the present study were tht mild OSA seems to be ssocited with cholesterol metbolism independent of BMI nd HOMA-IR. Secondly, one-yer weight reduction progrm resulted in chnges in cholesterol metbolism. Thirdly, fter weight reduction the improvement in OSA ws ssocited with chnges in cholesterol metbolism independent of weight nd HOMA-IR reductions. Weight reduction chieved by intensive lifestyle counselling with n initil VLCD progrm incresed S O2 nd serum cholestnol : cholesterol rtio suggesting tht cholesterol bsorption ws incresed. In ddition, AHI nd serum cholestenol : cholesterol rtio ws decresed suggesting tht cholesterol synthesis ws downregulted. Similr findings regrding cholesterol metbolism were reported in in type 2dibetics[21, 22]. The present study lso demonstrted tht ll these chnges sustined up to 1 yer. The negtive interreltions of cholesterol synthesis nd bsorption mrkers t bseline nd fter one yer (dt not shown) suggest tht cholesterol homeostsis remined intct irrespective of the intervention. There is definite need for further reserch to better understnd the links between OSA nd lipid metbolism nd b to improve the current guidelines of tretment. Thus fr, the interventionl studies exmining the effects of OSA tretment onlipidmetbolismhveexclusivelybeenconductedwith continuous positive irwy pressure (CPAP). However, the evidenceoftheeffectsofcpaptretmentondyslipidemiis limited. In one recent study, CPAP hs been demonstrted to reduce postprndil serum triglyceride nd totl cholesterol concentrtions [27] nd in nother, fsting serum cholesterol, but not triglyceride concentrtions [28]. The consensus sttement of Interntionl Dibetes Federtion highly recommends further reserch on OSA nd metbolism in generl nd prticulrly intervention studies with emphsis on crdiovsculr risk fctors, lso without using CPAP [29]. The sttement concludes tht mngement of OSA should focus initilly on weight reduction for the overweight nd obese. In generl, weight reduction improves serum lipid profile [30]. In the present study, weight reduction did not chnge serum totl nd LDL cholesterol concentrtions even though it ffected cholesterol metbolism. In niml models, IH ws suggested to induce dyslipidemi by upregulting biosynthesis of VLDL in liver, incresing lipolysis in dipocytes, nd inhibiting lipoprotein clernce [31 34]. Recently, in ptients with OSA, heptic expression of steroyl CoA desturse, key enzyme of lipid biosynthesis, hs been demonstrted to increse in direct proportion to the severity of nocturnl IH [33]. In ddition, overexpression ws ssocited with mrked increse in plsm triglyceride nd LDL cholesterol concentrtions [33]. However, thus fr there is no consistent evidence supporting the reltionship between OSA nd dyslipidemi in humns [11 14]. Bsed on niml models, IH ws suggested not to ffect cholesterol biosynthesis, becuse there ws no effect on the key genes involved in cholesterol biosynthesis [32]. However, we found in the subjects with mild OSA tht S O2,oneofthe key crdiorespirtory vribles, ws positively ssocited with cholesterol bsorption (serum cmpesterol : cholesterol rtio) nd inversely with cholesterol synthesis (serum desmosterol : cholesterol rtio) t bseline suggesting tht the greter S O2, the greter the cholesterol bsorption nd the lower the cholesterol synthesis. These ssocitions were independent from gender, BMI nd HOMA-IR. In ddition, lthough AHI ws not significntly ssocited with cholesterol bsorption mrkers, it tended to be ssocited positively with cholesterol synthesis mrkers (cholestenol : cholesterol rtio, P = 0.062). In the whole study popultion, the greter the weight reduction, the greter the reductions in AHI nd serum cholestenol : cholesterol rtio nd the increses in S O2 nd serum cholestnol : cholesterol rtio. In ddition, the percentge chnge of AHI ws inversely ssocited with tht of cholesterol bsorption mrker (cholestnol) nd positively with the percentge chnge of cholesterol synthesis mrkers. This suggests tht the more AHI ws improved, the more cholesterol bsorption ws incresed nd cholesterol synthesis decresed. The ssocitions between cholestnol nd of the cholesterol synthesis mrker cholestenol nd AHI remined significnt fter djustment with gender nd the percentge chnges of BMI nd HOMA-IR. On the contrry, the reltionships between the percentge chnges of S O2

7 Cholesterol Chnge in cholestenol (%) Chnge in cholestnol (%) Chnge in AHI (%) () Chnge in AHI (%) (b) Figure 2: The ssocitions between the percentge chnges in pnoe-hypopnoe index (AHI) nd serum cholestenol ((), r = 0.589, P< 0.001, N=41) nd cholestnol rtios to cholesterol (10 2 x mmol/mol of cholesterol) ((b), r = 0.441, P = 0.004, N=41)inthecontrol(I) nd intervention ( )groups. nd cholesterol bsorption nd synthesis mrkers were to opposite directions thn with AHI, but the reltionships did not reched sttisticl significnce. Even mild OSA is ssocited with incresed ctivtion of the inflmmtory system nd risk for crdiovsculr morbidity, lthough the risk is more frequently ssocited with more severe degrees of the disese [8 10]. The exct underlying mechnisms explining the ssocition between crdiovsculr morbidity nd OSA re not fully understood, lthough multifctoril etiology is most likely [6]. It is suggested tht OSA my ccelerte therosclerosis ffecting the key risk fctors of therosclerosis. One of the proposed potentil meditors nd ccelertors of therosclerosis in OSAispostultedtobedysregultionoflipidmetbolismnd dyslipidemi. Cholesterol bsorption is low, nd cholesterol synthesis is high in obesity [17], insulin resistnce [35], nd type 2 dibetes even without obesity [36]. In type 2 dibetes, weight reduction incresed cholesterol bsorption nd downregulted cholesterol synthesis simultneously with improved glucose blnce [22]. Therefore, low bsorptionhigh synthesis of cholesterol might be protherogenic in insulin-resistnt situtions, possibly frequently present lso in OSA. This kind of metbolic profile of cholesterol of insulin resistnce is different from tht observed in primry hypercholesterolemi, in which high bsorption-low synthesis of cholesterol is ssocited with unfvorble prognosis during sttin tretment in coronry subjects [37]. The present study demonstrtes tht with weight reduction both OSA nd the possibly protherogenic profile of cholesterol metbolism cn be improved. The intriguing question, however, is by which mechnism the vribles of OSA nd cholesterol metbolismreinterreltedbeyondobesity.bothtbseline nd fter the intervention with improved tissue oxygention the ssocitions between OSA nd cholesterol metbolism were similr: better oxygention is ssocited with higher bsorption nd lower synthesis of cholesterol independent of BMI. Our study popultion ws homogenous consisting only of overweight subjects with mild OSA. Therefore, the results cnnot be generlized to ll OSA ptients, nd there exist lsosomelimittionsinthisstudy.thesmplesizeper group ws reltively smll, nd it ws smller thn in the originl study [20], becuse the subjects using lipidlowering mediction hd to be excluded. With lrger study popultion the results, which now tended to be significnt, might become significnt. Furthermore, the smple size of the present study is similr to those in other recent interventionl studies exmining lipid metbolisms in OSA ptients. Becuse no strtifiction in terms of BMI ws used in the rndomistion, the weight between the groups differed t bseline. Therefore, we djusted the results for the bseline BMI. Furthermore, becuse serum insulin concentrtion nd cholestenol : cholesterol rtio were greter nd HOMA-IR tended to significntly greter in the intervention group compred with controls t bseline, the bseline vlues were tkenintoccountscovrinceinthenlysesofthose vribles. Regrdless of some limittions, the present study is, s fr s we know, the first study to exmine the ssocitions between OSA nd cholesterol metbolism in humns nd with nd without lifestyle intervention in rndomised settings. Furthermore, this study demonstrted the even mild OSAseemedtobessocitedwithbnormlcholesterol metbolism. CPAP is considered s gold stndrd of OSA tretment [38]. However, the dherence of some ptients to CPAP tretment is unstisfctory, prticulrly in the erly stges of the OSA. Bsed on the recent rndomised studies nd on the fct tht obesity is the most importnt risk fctor for OSA nd most OSA ptients re obese, weight reduction by lifestyle chnges (helthy eting hbits, food behviour therpy if

8 8 Cholesterol needed nd physicl ctivity) should be the first line or t lestprtofthetretmentforlloverweightosaptients. Besides improving OSA, weight reduction seems to improve lso other obesity-relted disturbnces of crdiometbolic syndrome [20, 39]. In conclusion, weight reduction with intensive lifestyle counselling with n initil VLCD progrm incresed the mrkers of cholesterol bsorption nd decresed those of cholesterol synthesis in subjects with mild OSA. High S O2 seems to be ssocited with high cholesterol bsorption nd low S O2 with upregulted cholesterol synthesis independent of BMI, HOMA-IR, nd gender. Improvement in AHI ws ssocited with incresed cholesterol bsorption nd decresed cholesterol synthesis independent of BMI nd HOMA-IR. However, further studies with greter number of subjects re needed to confirm these results. Conflict of Interests The uthors declre no conflict of interests. Acknowledgments The members of Kuopio Sleep Apnoe Group Tin Poutiinen, Grigori Smirnov, Tomi Litinen, Tiin Lyyr-Litinen, Mtti Uusitup, Aki Ikonen, Ritv Vnninen, Heimo Viinmäki, Keijo Peuhkurinen, Kri Punnonen, Erkki Soini, nd Jnne Mrtikinen re cordilly cknowledged. The uthors thnk lso Erj Kinnunen for excellent lbortory work.thestudywsfundedbythehospitldistrictof NorthernSvo.KuopioUniversityHospitl,theJuhoVinio Foundtion, Pvo Nurmi Foundtion, nd the Finnish Anti- Tuberculosis Foundtion hve supported the study with grnts. The funding sources hd no role in study design; collection, nlysis, or interprettion of the dt; or writing of the report. References [1] T. Young, P. E. Pepprd, nd D. J. Gottlieb, Epidemiology of obstructive sleep pne: popultion helth perspective, Americn Journl of Respirtory nd Criticl Cre Medicine,vol. 165, no. 9, pp , [2] S. R. Coughlin, L. Mwdsley, J. A. Mugrz, P. M. A. Clverley, ndj.p.h.wilding, Obstructivesleeppnoeisindependently ssocited with n incresed prevlence of metbolic syndrome, Europen Hert Journl, vol.25,no.9,pp , [3]F.J.Nieto,T.B.Young,B.K.Lindetl., Associtionof sleep-disordered brething sleep pne, nd hypertension in lrge community-bsed study, Journl of the Americn Medicl Assocition,vol.283,no.14,pp ,2000. [4] P.E.Pepprd,T.Young,M.Plt,ndJ.Sktrud, Prospective study of the ssocition between sleep-disordered brething nd hypertension, The New Englnd Journl of Medicine, vol. 342,no.19,pp ,2000. [5] E. Shhr, C. W. Whitney, S. Redline et l., Sleep-disordered brething nd crdiovsculr disese: cross-sectionl results of the sleep hert helth study, Americn Journl of Respirtory nd Criticl Cre Medicine,vol.163,no.1,pp.19 25,2001. [6] A. S. M. Shmsuzzmn, B. J. Gersh, nd V. K. Somers, Obstructive sleep pne: implictions for crdic nd vsculr disese, JournloftheAmericnMediclAssocition, vol. 290, no.14,pp ,2003. [7] H. Tuomilehto, M. Peltonen, M. Prtinen et l., Sleepdisordered brething is relted to n incresed risk for type 2 dibetes in middle-ged men, but not in women -the FIN-D2D survey, Dibetes, Obesity nd Metbolism, vol. 10, no. 6, pp , [8] N.M.Punjbi,B.S.Cffo,J.L.Goodwinetl., Sleep-disordered brething nd mortlity: A Prospective Cohort Study, PLoS Medicine,vol.6,no.8,rticlee ,2009. [9] M. Prtinen nd C. Guilleminult, Dytime sleepiness nd vsculr morbidity t seven-yer follow-up in obstructive sleep pne ptients, Chest, vol. 97, no. 1, pp , [10] J. Shlmn, K. Miettinen, K. Peuhkurinen et l., The ctivtion of the inflmmtory cytokines in overweight ptients with mild obstructive sleep pnoe: sleep pne nd inflmmtion, Journl of Sleep Reserch,vol.19,no.2,pp ,2010. [11] A. B. Newmn, F. J. Nieto, U. Guidry et l., Reltion of sleepdisordered brething to crdiovsculr disese risk fctors: The Sleep Hert Helth Study, Americn Journl of Epidemiology, vol.154,no.1,pp.50 59,2001. [12] F. Roche, E. Sforz, V. Pichot et l., Obstructive sleep pnoe/hypopne influences high-density lipoprotein cholesterol in the elderly, Sleep Medicine, vol. 10, no. 8, pp , [13] C. Tsioufis, K. Thomopoulos, K. Dimitridis et l., The incrementl effect of obstructive sleep pnoe syndrome on rteril stiffness in newly dignosed essentil hypertensive subjects, Journl of Hypertension,vol.25,no.1,pp ,2007. [14] L. F. Drger, L. A. Bortolotto, M. C. Lorenzi, A. C. Figueiredo, E. M. Krieger, nd G. Lorenzi-Filho, Erly signs of therosclerosis in obstructive sleep pne, Americn Journl of Respirtory nd Criticl Cre Medicine,vol.172,no.5,pp ,2005. [15] L. F. Drger, V. Y. Polotsky, nd G. Lorenzi-Filho, Obstructive sleep pne: n emerging risk fctor for therosclerosis, Chest, vol. 140, no. 2, pp , [16] T. Young, J. Sktrud, nd P. E. Pepprd, Risk fctors for obstructive sleep pne in dults, Journl of the Americn Medicl Assocition,vol.291,no.16,pp ,2004. [17] T. A. Miettinen nd H. Gylling, Cholesterol bsorption efficiency nd sterol metbolism in obesity, Atherosclerosis, vol. 153, no. 1, pp , [18] H. Gylling, M. Hllikinen, M. Kolehminen et l., Cholesterol synthesis previls over bsorption in metbolic syndrome, Trnsltionl Reserch,vol.149,no.6,pp ,2007. [19] G. Pillr nd N. Shehdeh, Abdominl ft nd sleep pne: the chicken or the egg? Dibetes Cre, vol. 31, pp. S303 S309, [20] H. P. I. Tuomilehto, J. M. Seppä, M. M. Prtinen et l., Lifestyle intervention with weight reduction: first-line tretment in mild obstructive sleep pne, Americn Journl of Respirtory nd Criticl Cre Medicine,vol.179,no.4,pp ,2009. [21] P. Simonen, H. Gylling, nd T. A. Miettinen, Acute effects of weight reduction on cholesterol metbolism in obese type 2 dibetes, Clinic Chimic Act, vol. 316, no. 1-2, pp , [22] P. Simonen, H. Gylling, A. N. Howrd, nd T. A. Miettinen, Introducing new component of the metbolic syndrome: low cholesterol bsorption, Americn Journl of Clinicl Nutrition, vol. 72, no. 1, pp , 2000.

9 Cholesterol 9 [23] T. A. Miettinen, R. S. Tilvis, nd Y. A. Kesäniemi, Serum plnt sterols nd cholesterol precursors reflect cholesterol bsorption nd synthesis in volunteers of rndomly selected mle popultion, Americn Journl of Epidemiology, vol.131,no.1,pp , [24] W. W. Flemons, D. Buysse, S. Redline et l., Sleep-relted brething disorders in dults: recommendtions for syndrome definition nd mesurement techniques in clinicl reserch, Sleep,vol.22,no.5,pp ,1999. [25] D.R.Mtthews,J.P.Hosker,ndA.S.Rudenski, Homeostsis model ssessment: Insulin resistnce nd β-cell function from fsting plsm glucose nd insulin concentrtions in mn, Dibetologi,vol.28,no.7,pp ,1985. [26] T. A. Miettinen, Cholesterol metbolism during ketoconzole tretment in mn, Journl of Lipid Reserch, vol.29,no.1,pp , [27] C. L. Phillips, B. J. Yee, N. S. Mrshll, P. Y. Liu, D. R. Sullivn, nd R. R. Grunstein, Continuous positive irwy pressure reduces postprndil lipidemi in obstructive sleep pne: rndomized, plcebo-controlled crossover tril, Americn Journl of Respittory nd Criticl Cre Medicine, vol.184,no. 3, pp , [28] G.V.Robinson,J.C.T.Pepperell,H.C.Segl,R.J.O.Dvies, nd J. R. Strdling, Circulting crdiovsculr risk fctors in obstructive sleep pnoe: dt from rndomised controlled trils, Thorx,vol.59,no.9,pp ,2004. [29] J. E. Shw, N. M. Punjbi, J. P. Wilding, K. G. M. M. Alberti, nd P. Z. Zimmet, Sleep-disordered brething nd type 2 dibetes. A report from the Interntionl Dibetes Federtion Tskforce on Epidemiology nd Prevention, Dibetes Reserch nd Clinicl Prctice,vol.81,no.1,pp.2 12,2008. [30] A. M. Dttilo nd P. M. Kris-Etherton, Effects of weight reduction on blood lipids nd lipoproteins: met- nlysis, Americn Journl of Clinicl Nutrition, vol.56,no.2,pp , [31] J.Li,V.Svrnsky,A.Nnykkr,P.L.Smith,C.P.O Donnell, nd V. Y. Polotsky, Hyperlipidemi nd lipid peroxidtion re dependent on the severity of chronic intermittent hypoxi, Journl of Applied Physiology,vol.102,no.2,pp ,2007. [32] J.Li,L.N.Thorne,N.M.Punjbietl., Intermittenthypoxi induces hyperlipidemi in len mice, Circultion Reserch,vol. 97, no. 7, pp , [33] V. Svrnsky, J. Jun, J. Li et l., Dyslipidemi nd therosclerosis induced by chronic intermittent hypoxi re ttenuted by deficiency of steroyl coenzyme desturse, Circultion Reserch, vol. 103, no. 10, pp , [34] L. F. Drger, J. Li, M. K. Shin et l., Intermittent hypoxi inhibits clernce of triglyceride-rich lipoproteins nd inctivtes dipose lipoprotein lipse in mouse model of sleep pnoe, Europen Hert Journl, vol. 19, no. 11, pp , [35] J. Pihljmäki, H. Gylling, T. A. Miettinen, nd M. Lkso, Insulin resistnce is ssocited with incresed cholesterol synthesis nd decresed cholesterol bsorption in normoglycemic men, Journl of Lipid Reserch, vol. 45, no. 3, pp , [36] P. P. Simonen, H. K. Gylling, nd T. A. Miettinen, Dibetes contributes to cholesterol metbolism regrdless of obesity, Dibetes Cre,vol.25,no.9,pp ,2002. [37] T. A. Miettinen, H. Gylling, T. Strndberg, nd S. Srn, Bseline serum cholestnol s predictor of recurrent coronry events in subgroup of Scndinvin simvsttin survivl study, British Medicl Journl,vol.316,no.7138,pp ,1998. [38] E. Bllester, J. R. Bdi, L. Hernández et l., Evidence of the effectiveness of continuous positive irwy pressure in the tretment of sleep pne/hypopne syndrome, Americn Journl of Respirtory nd Criticl Cre Medicine, vol.159,no. 2,pp ,1999. [39] K. Johnsson, E. Hemmingsson, R. Hrlid et l., Longer term effects of very low energy diet on obstructive sleep pnoe in cohort derived from rndomised controlled tril: Prospective Observtionl Follow-up Study, British Medicl Journl, vol. 342, no. d3017, 2011.

10 MEDIATORS of INFLAMMATION The Scientific World Journl Gstroenterology Reserch nd Prctice Journl of Dibetes Reserch Interntionl Journl of Journl of Endocrinology Immunology Reserch Disese Mrkers Submit your mnuscripts t BioMed Reserch Interntionl PPAR Reserch Journl of Obesity Journl of Ophthlmology Evidence-Bsed Complementry nd Alterntive Medicine Stem Cells Interntionl Journl of Oncology Prkinson s Disese Computtionl nd Mthemticl Methods in Medicine AIDS Behviourl Neurology Reserch nd Tretment Oxidtive Medicine nd Cellulr Longevity