Metabolic effects of alternate-day fasting in males with obesity with or without type 2 diabetes

Alternate-day fasting induces oscillations in energy stores. We hypothesized that repeated oscillations increases insulin secretion and sensitivity, and improve metabolic health in patients with obesity with or without type 2 diabetes (T2DM). Twenty-three male patients fasted every other day for 30 h for 6 weeks. Experiments included resting energy expenditure, continuous glucose monitoring, intravenous glucose tolerance test, euglycemic hyperinsulinemic clamp, body composition, hepatic triglyceride content, muscle biopsies which were performed at baseline, during 3 weeks without allowed weight loss, and after additional 3 weeks with weight loss. Bodyweight decreased ∼1% and further ∼3% during weeks one to three and four to six, respectively (p < 0.05). Only minor changes in fat mass occurred in weeks 1-3. With weight loss, visceral fat content decreased by 13 ± 3% and 12 ± 2% from baseline in patients with and without T2DM, respectively (p < 0.05). Hepatic triglyceride content decreased by 17 ± 9% and 36 ± 9% (with diabetes) and 27 ± 8% and 40 ± 8% (without diabetes) from baseline to week 3 and week 6, respectively (all p < 0.05). Muscle lipid and glycogen content oscillated with the intervention. Glucose homeostasis, insulin secretion and sensitivity was impaired in patients with T2DM and did not change without weight loss, but improved (p < 0.05) when alternate day fasting was combined with weight loss. In conclusion, alternate-day fasting is feasible in patients with obesity and T2DM, and decreases visceral fat and liver fat deposits. Energy store oscillations by alternate-day fasting do not improve insulin secretion or sensitivity per se. Clinical Trial registration: (ClinicalTrials.gov), (ID NCT02420054).

Repeated Prolonged Exercise Decreases Maximal Fat Oxidation in Older Men

INTRODUCTION/PURPOSE

Fat metabolism and muscle adaptation was investigated in six older trained men (age, 61 ± 4 yr; V˙O2max, 48 ± 2 mL·kg·min) after repeated prolonged exercise).

METHODS

A distance of 2706 km (1681 miles) cycling was performed over 14 d, and a blood sample and a muscle biopsy were obtained at rest after an overnight fast before and 30 h after the completion of the cycling. V˙O2max and maximal fat oxidation were measured using incremental exercise tests. HR was continuously sampled during cycling to estimate exercise intensity.

RESULTS

The daily duration of exercise was 10 h and 31 ± 37 min, and the mean intensity was 53% ± 1% of V˙O2max. Body weight remained unchanged. V˙O2max and maximal fat oxidation rate decreased by 6% ± 2% (P = 0.04) and 32% ± 8% (P < 0.01), respectively. The exercise intensity that elicits maximal fat oxidation was not significantly decreased. Plasma free fatty acid (FA) concentration decreased (P < 0.002) from 500 ± 77 μmol·L to 160 ± 38 μmol·L. Plasma glucose concentration as well as muscle glycogen, myoglobin, and triacylglycerol content remained unchanged. Muscle citrate synthase and ß-hydroxy-acyl-CoA-dehydrogenase activities were unchanged, but the protein expression of HKII, GLUT4, and adipose triacylglycerol lipase were significantly increased.

CONCLUSIONS

Overall, the decreased maximal fat oxidation was probably due to lower exogenous plasma fatty acid availability and the muscle adaptation pattern indicates an increased glucose transport capacity and an increased muscle lipolysis capacity supporting an increased contribution of exogenous glucose and endogenous fat during exercise.

A novel method for determining human ex vivo submaximal skeletal muscle mitochondrial function

The present study utilized a novel method aiming to investigate mitochondrial function in human skeletal muscle at submaximal levels and at a predefined membrane potential. The effect of age and training status was investigated using a cross-sectional design. Ageing was found to be related to decreased leak regardless of training status. Increased training status was associated with increased mitochondrial hydrogen peroxide emission. Despite numerous studies, there is no consensus about whether mitochondrial function is altered with increased age. The novelty of the present study is the determination of mitochondrial function at submaximal activity rates, which is more physiologically relevant than the ex vivo functionality protocols used previously. Muscle biopsies were taken from 64 old or young male subjects (aged 60-70 or 20-30 years). Aged subjects were recruited as trained or untrained. Muscle biopsies were used for the isolation of mitochondria and subsequent measurements of DNA repair, anti-oxidant capacity and mitochondrial protein levels (complexes I-V). Mitochondrial function was determined by simultaneous measurement of oxygen consumption, membrane potential and hydrogen peroxide emission using pyruvate + malate (PM) or succinate + rotenone (SR) as substrates. Proton leak was lower in aged subjects when determined at the same membrane potential and was unaffected by training status. State 3 respiration was lower in aged untrained subjects. This effect, however, was alleviated in aged trained subjects. H2 O2 emission with PM was higher in aged subjects, and was exacerbated by training, although it was not changed when using SR. However, with a higher manganese superoxide dismuthase content, the trained aged subjects may actually have lower or similar mitochondrial superoxide emission compared to the untrained subjects. We conclude that ageing and the physical activity level in aged subjects are both related to changes in the intrinsic functionality of the mitochondrion in skeletal muscle. Both of these changes could be important factors in determining the metabolic health of the aged skeletal muscle cell.

GAPDH and β-actin protein decreases with aging, making Stain-Free technology a superior loading control in Western blotting of human skeletal muscle

Reference proteins (RP) or the total protein (TP) loaded is used to correct for uneven loading and/or transfer in Western blotting. However, the signal sensitivity and the influence of physiological conditions may question the normalization methods. Therefore, three widely used reference proteins [β-actin, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and α-tubulin], as well as TP loaded measured by Stain-Free technology (SF) as normalization tool were tested. This was done using skeletal muscle samples from men subjected to physiological conditions often investigated in applied physiology where the intervention has been suggested to impede normalization (ageing, muscle atrophy, and different muscle fiber type composition). The linearity of signal and the methodological variation coefficient was obtained. Furthermore, the inter- and intraindividual variation in signals obtained from SF and RP was measured in relation to ageing, muscle atrophy, and different muscle fiber type composition, respectively. A stronger linearity of SF and β-actin compared with GAPDH and α-tubulin was observed. The methodological variation was relatively low in all four methods (4-11%). Protein level of β-actin and GAPDH was lower in older men compared with young men. In conclusion, β-actin, GAPDH, and α-tubulin may not be used for normalization in studies that include subjects with a large age difference. In contrast, the RPs may not be affected in studies that include muscle wasting and differences in muscle fiber type. The novel SF technology adds lower variation to the results compared with the existing methods for correcting for loading inaccuracy in Western blotting of human skeletal muscle in applied physiology.

Two weeks of one-leg immobilization decreases skeletal muscle respiratory capacity equally in young and elderly men

Physical inactivity affects human skeletal muscle mitochondrial oxidative capacity but the influence of aging combined with physical inactivity is not known. This study investigates the effect of two weeks of immobilization followed by six weeks of supervised cycle training on muscle oxidative capacity in 17 young (23±1years) and 15 elderly (68±1years) healthy men. We applied high-resolution respirometry in permeabilized fibers from muscle biopsies at inclusion after immobilization and training. Furthermore, protein content of mitochondrial complexes I-V, mitochondrial heat shock protein 70 (mtHSP70) and voltage dependent anion channel (VDAC) were measured in skeletal muscle by Western blotting. The elderly men had lower content of complexes I-V and mtHSP70 but similar respiratory capacity and content of VDAC compared to the young. In both groups the respiratory capacity and protein content of VDAC, mtHSP70 and complexes I, II, IV and V decreased with immobilization and increased with retraining. Moreover, there was no overall difference in the response between the groups. When the intrinsic mitochondrial capacity was evaluated by normalizing respiration to citrate synthase activity, the respiratory differences with immobilization and training disappeared. In conclusion, aging is not associated with a decrease in muscle respiratory capacity in spite of lower complexes I-V and mtHSP70 protein content. Furthermore, immobilization decreased and aerobic training increased the respiratory capacity and protein contents of complexes I-V, mtHSP70 and VDAC similarly in the two groups. This suggests that inactivity and training alter mitochondrial biogenesis equally in young and elderly men.

Biomarkers of mitochondrial content in skeletal muscle of healthy young human subjects

Skeletal muscle mitochondrial content varies extensively between human subjects. Biochemical measures of mitochondrial proteins, enzyme activities and lipids are often used as markers of mitochondrial content and muscle oxidative capacity (OXPHOS). The purpose of this study was to determine how closely associated these commonly used biochemical measures are to muscle mitochondrial content and OXPHOS. Sixteen young healthy male subjects were recruited for this study. Subjects completed a graded exercise test to determine maximal oxygen uptake (VO2peak) and muscle biopsies were obtained from the vastus lateralis. Mitochondrial content was determined using transmission electron microscopy imaging and OXPHOS was determined as the maximal coupled respiration in permeabilized fibres. Biomarkers of interest were citrate synthase (CS) activity, cardiolipin content, mitochondrial DNA content (mtDNA), complex I–V protein content, and complex I–IV activity. Spearman correlation coefficient tests and Lin's concordance tests were applied to assess the absolute and relative association between the markers and mitochondrial content or OXPHOS. Subjects had a large range of VO2peak (range 29.9–71.6ml min−1 kg−1) and mitochondrial content (4–15% of cell volume).Cardiolipin content showed the strongest association with mitochondrial content followed by CS and complex I activities. mtDNA was not related to mitochondrial content. Complex IV activity showed the strongest association with muscle oxidative capacity followed by complex II activity.We conclude that cardiolipin content, and CS and complex I activities are the biomarkers that exhibit the strongest association with mitochondrial content, while complex IV activity is strongly associated with OXPHOS capacity in human skeletal muscle.

5'-AMP Activated Protein Kinase is Involved in the Regulation of Myocardial β-Oxidative Capacity in Mice

5′-adenosine monophosphate-activated protein kinase (AMPK) is considered central in regulation of energy status and substrate utilization within cells. In heart failure the energetic state is compromised and substrate metabolism is altered. We hypothesized that this could be linked to changes in AMPK activity and we therefore investigated mitochondrial oxidative phosphorylation capacity from the oxidation of long- and medium-chain fatty acids (LCFA and MCFA) in cardiomyocytes from young and old mice expressing a dominant negative AMPKα2 (AMPKα2-KD) construct and their wildtype (WT) littermates. We found a 35–45% (P < 0.05) lower mitochondrial capacity for oxidizing MCFA in AMPKα2-KD of both age-groups, compared to WT. This coincided with marked decreases in protein expression (19/29%, P < 0.05) and activity (14/21%, P < 0.05) of 3-hydroxyacyl-CoA-dehydrogenase (HAD), in young and old AMPKα2-KD mice, respectively, compared to WT. Maximal LCFA oxidation capacity was similar in AMPKα2-KD and WT mice independently of age implying that LCFA-transport into the mitochondria was unaffected by loss of AMPK activity or progressing age. Expression of regulatory proteins of glycolysis and glycogen breakdown showed equivocal effects of age and genotype. These results illustrate that AMPK is necessary for normal mitochondrial function in the heart and that decreased AMPK activity may lead to an altered energetic state as a consequence of reduced capacity to oxidize MCFA. We did not identify any clear aging effects on mitochondrial function.

Metformin-treated patients with type 2 diabetes have normal mitochondrial complex I respiration

AIMS/HYPOTHESIS

The glucose-lowering drug metformin has been shown to inhibit complex I of the mitochondrial electron transport chain in skeletal muscle. To investigate this effect in vivo we studied skeletal muscle mitochondrial respiratory capacity and content from patients with type 2 diabetes treated with metformin (n = 14) or sulfonylurea (n = 8) and healthy control (n = 18) participants.

METHODS

Mitochondrial respiratory capacity was measured ex vivo in permeabilised muscle fibres obtained from the vastus lateralis muscle of all participants. The respiratory response to in vitro titration with metformin was measured in controls. Citrate synthase (CS) activity, and fasting plasma glucose, insulin and HbA(1c) levels were measured and body composition was determined.

RESULTS

Participants were matched for age, BMI and percentage body fat. Fasting plasma glucose concentrations were higher (p < 0.05) in those treated with sulfonylureas and metformin than in controls. CS activity was comparable between metformin-treated and control participants, but tended to be lower in those receiving sulfonylureas. Mitochondrial respiratory capacity with substrates for complex I and complex I and II was comparable in the groups, both when estimated per mg of tissue and when normalised to CS activity. In vitro metformin titration demonstrated a dose-dependent inhibitory effect on complex I and II in human skeletal muscle at suprapharmacological concentrations.

CONCLUSIONS/INTERPRETATION

Metformin treatment does not inhibit mitochondrial complex I respiration in the electron transport chain in human skeletal muscle of patients with type 2 diabetes when measured ex vivo. Inhibition of complex I and II respiration in controls was demonstrated by metformin titration in vitro at doses well above those observed during metformin treatment.

Increased mitochondrial substrate sensitivity in skeletal muscle of patients with type 2 diabetes

AIMS/HYPOTHESIS

Mitochondrial respiration has been linked to insulin resistance. We studied mitochondrial respiratory capacity and substrate sensitivity in patients with type 2 diabetes (patients), and obese and lean control participants.

METHODS

Mitochondrial respiration was measured in permeabilised muscle fibres by respirometry. Protocols for respirometry included titration of substrates for complex I (glutamate), complex II (succinate) and both (octanoyl-carnitine). Myosin heavy chain (MHC) composition, antioxidant capacity (manganese superoxide dismutase [MnSOD]), citrate synthase activity and maximal oxygen uptake (VO2) were also determined. Insulin sensitivity was determined with the isoglycaemic-hyperinsulinaemic clamp technique.

RESULTS

Insulin sensitivity was different (p < 0.05) between the groups (patients<obese controls<lean controls). MnSOD was lower in patients than in lean controls. MHC I content was lowest in patients (37 ± 11% [mean ± SE] vs 53 ± 6% and 56 ± 4%) vs obese controls and lean controls, respectively. VO2 was highest in lean controls (40 ± 3 ml min(-1) kg(-1) [mean ± SE]) compared with patients (25 ± 2) and obese controls (27 ± 2). Mitochondrial content (citrate synthase) was higher (p < 0.05) in lean controls than in patients and obese controls. When normalised for mitochondrial content by citrate synthase, mitochondrial respiratory capacity was similar in all groups. However, the half maximal substrate concentration (C(50)) for complex I was significantly lower (p = 0.03) in patients (1.1 ± 0.2 mmol/l [mean ± SE]) than in obese (2.0 ± 0.3) and lean (1.8 ± 0.3) controls. Likewise, C(50) for complex II was lower (p = 0.02) in patients (3.5 ± 0.2 mmol/l [mean ± SE]) than in obese controls (4.1 ± 0.2), but did not differ from that in lean controls (3.8 ± 0.4). Substrate sensitivity for octanoyl-carnitine did not differ between groups.

CONCLUSIONS/INTERPRETATION

Increased mitochondrial substrate sensitivity is seen in skeletal muscle from type 2 diabetic patients and is confined to non-lipid substrates. Respiratory capacity per mitochondrion is not decreased with insulin resistance.

High-fat feeding inhibits exercise-induced increase in mitochondrial respiratory flux in skeletal muscle

Twenty one healthy untrained male subjects were randomized to follow a high-fat diet (HFD; 55-60E% fat, 25-30E% carbohydrate, and 15E% protein) or a normal diet (ND; 25-35E% fat, 55-60E% carbohydrate, and 10-15E% protein) for 2(1/2) wk. Diets were isocaloric and tailored individually to match energy expenditure. At 2(1/2) wk of diet, one 60-min bout of bicycle exercise (70% of maximal oxygen uptake) was performed. Muscle biopsies were obtained before and after the diet, immediately after exercise, and after 3-h recovery. Insulin sensitivity (hyperinsulinemic-euglycemic clamp) and intramyocellular triacylglycerol content did not change with the intervention in either group. Indexes of mitochondrial density were similar across the groups and intervention. Mitochondrial respiratory rates, measured in permeabilized muscle fibers, showed a 31 ± 11 and 26 ± 9% exercise-induced increase (P < 0.05) in state 3 (glycolytic substrates) and uncoupled respiration, respectively. However, in HFD this increase was abolished. At recovery, no change from resting respiration was seen in either group. With a lipid substrate (octanoyl-carnitine with or without ADP), similar exercise-induced increases (31-62%) were seen in HFD and ND, but only in HFD was an elevated (P < 0.05) respiratory rate seen at recovery. With HFD complex I and IV protein expression decreased (P < 0.05 and P = 0.06, respectively). A fat-rich diet induces marked changes in the mitochondrial electron transport system protein content and in exercise-induced mitochondrial substrate oxidation rates, with the effects being present hours after the exercise. The effect of HFD is present even without effects on insulin sensitivity and intramyocellular lipid accumulation. An isocaloric high-fat diet does not cause insulin resistance.

Opposite effects of pioglitazone and rosiglitazone on mitochondrial respiration in skeletal muscle of patients with type 2 diabetes

AIM

Skeletal muscle insulin resistance has been linked to mitochondrial dysfunction. We examined how improvements in muscular insulin sensitivity following rosiglitazone (ROSI) or pioglitazone (PIO) treatment would affect muscle mitochondrial function in patients with type 2 diabetes mellitus (T2DM).

METHODS

Muscle biopsies were obtained from 21 patients with T2DM before and after 12 weeks on either ROSI (4 mg once daily) [n = 12; age, 59.2 +/- 2.2 years; body mass index (BMI), 29.6 +/- 0.7 kg/m(2)] or PIO (30 mg once daily) (n = 9; age, 56.3 +/- 2.4 years; BMI, 29.5 +/- 1.5 kg/m(2)). An age- and BMI-matched control group was also included (n = 8; age, 61.8 +/- 2.3 years; BMI, 28.4 +/- 0.6 kg/m(2)). Insulin sensitivity, citrate synthase- and beta-hydroxyacyl-CoA-dehydrogenase (HAD) activity, intramuscular triglyceride (IMTG) and protein content of complexes I-IV were measured, while mitochondrial respiration per milligram muscle was measured in saponin-treated skinned muscle fibres using high-resolution respirometry.

RESULTS

Mitochondrial respiration per milligram muscle was lower in T2DM compared to controls at baseline and decreased during ROSI treatment but increased during PIO treatment. Citrate synthase activity and average protein content of complexes I-IV were unchanged in the ROSI group, but protein content of complexes II and III increased during PIO treatment. Insulin sensitivity improved in all patients, but IMTG levels were unchanged.

CONCLUSIONS

We show opposite effects of ROSI and PIO on mitochondrial respiration, and also show that insulin sensitivity can be improved independently of changes in mitochondrial respiration. We confirm that mitochondrial respiration is reduced in T2DM compared to age- and BMI-matched control subjects.

Mitochondrial respiration in subcutaneous and visceral adipose tissue from patients with morbid obesity

Adipose tissue exerts important endocrine and metabolic functions in health and disease. Yet the bioenergetics of this tissue is not characterized in humans and possible regional differences are not elucidated. Using high resolution respirometry, mitochondrial respiration was quantified in human abdominal subcutaneous and intra-abdominal visceral (omentum majus) adipose tissue from biopsies obtained in 20 obese patients undergoing bariatric surgery. Mitochondrial DNA (mtDNA) and genomic DNA (gDNA) were determined by the PCR technique for estimation of mitochondrial density. Adipose tissue samples were permeabilized and respirometric measurements were performed in duplicate at 37 degrees C. Substrates (glutamate (G) + malate (M) + octanoyl carnitine (O) + succinate (S)) were added sequentially to provide electrons to complex I + II. ADP ((D)) for state 3 respiration was added after GM. Uncoupled respiration was measured after addition of FCCP. Visceral fat contained more mitochondria per milligram of tissue than subcutaneous fat, but the cells were smaller. Robust, stable oxygen fluxes were found in both tissues, and coupled state 3 (GMOS(D)) and uncoupled respiration were significantly (P < 0.05) higher in visceral (0.95 +/- 0.05 and 1.15 +/- 0.06 pmol O(2) s(1) mg(1), respectively) compared with subcutaneous (0.76 +/- 0.04 and 0.98 +/- 0.05 pmol O(2) s(1) mg(1), respectively) adipose tissue. Expressed per mtDNA, visceral adipose tissue had significantly (P < 0.05) lower mitochondrial respiration. Substrate control ratios were higher and uncoupling control ratio lower (P < 0.05) in visceral compared with subcutaneous adipose tissue. We conclude that visceral fat is bioenergetically more active and more sensitive to mitochondrial substrate supply than subcutaneous fat. Oxidative phosphorylation has a higher relative activity in visceral compared with subcutaneous adipose tissue.

Activities of E7 promoters in the human papillomavirus type 16 genome during cell differentiation

Worldwide, one of the most common cancer forms diagnosed in women is cervical cancer induced by infections with high-risk human papillomaviruses (HPVs) with HPV type 16 (HPV-16) being the most frequently identified. The oncogenicity is caused mainly by expression of the oncogenes E6 and E7 leading to deregulation of the cell cycle control. HPV-16 preferably infects the proliferating cells that will differentiate when they move upwards in the epithelium. The viral gene-expression is tightly coupled to the cellular differentiation program with early gene-expression being initiated in non- or low-differentiated cells and late gene-expression in more differentiated cells. We induced epithelial cells to differentiate by growth in medium with a high calcium concentration and measured the activity of different promoters thought to initiate E6 and/or E7 transcripts. The overall activity of the main promoter, P97, situated in the long control region as well as the two promoters, P441 and P542, in the E6 ORF upstream of the E7 ORF, were decreased during differentiation. However, P441 and P542 were not down-regulated as much as P97. Therefore, we suggest that P441 and P542 regulate gene-expression in differentiated cells.

Characterisation of pararetrovirus-like sequences in the genome of potato (Solanum tuberosum)

Three families of pararetrovirus-like sequences were isolated from the genome of potato using PCR of a characteristic fragment extending from the end of the transactivator domain. The potato pararetrovirus-like sequences are abundant in the nuclear genome of potato as demonstrated by their hybridisation to high-molecular weight DNA in Southern transfers and by fluorescence in situ hybridisation. Sequencing of cloned PCR products demonstrated that the potato pararetrovirus-like sequences were similar to other pararetroviral sequences and also to some expressed sequences from tobacco and tomato, notably from callus and Agrobacterium-infected tissue. It is possible that the potato pararetroviral sequences defend against viral genes via silencing mechanisms, although, as in Petunia or banana, their transcription and recombination may cause infection under stress conditions.

Twelve years' clinical experience with the CarboMedics prosthetic heart valve

BACKGROUND AND AIM OF THE STUDY

The CarboMedics bileaflet prosthetic heart valve was first implanted as part of a prospective clinical study at the authors' institution in November 1987. The patient cohort included was part of a multicenter trial set up by the manufacturer for an FDA application. The present report details findings over a 12-year period, with a continuous follow up on this patient cohort.

METHODS

Between November 1987 and August 1990, 132 patients (68 males, 64 females; median age 56 years; range 12-74 years) received a CarboMedics heart valve prosthesis. All patients were included in the study, whether surgery was elective or emergency, first time or reoperation. There were 69 aortic, 49 mitral and 12 double (aortic + mitral) valve replacements. Two patients had isolated tricuspid valve replacement. Concomitant surgery was performed in 15 patients. Anticoagulation with warfarin was started on postoperative day 1. After discharge, patients were examined regularly as outpatients for up to five years. Subsequent follow up was obtained prospectively by questionnaires to the patients' general practitioner, or by telephone calls. Actuarial estimates of survival and freedom from morbid events were calculated using the Kaplan-Meier method; 95% confidence limits for the distribution function were calculated according to the Greenwood formula.

RESULTS

Complete follow up information was available for 94% of the patients; total follow up was 1,014.3 patient-years (pt-yr). Actuarial survival at 12 years was 62 +/- 0.5% overall (61 +/- 6.5% for aortic; 66 +/- 7.5% for mitral; 65 +/- 14.0% for double valve replacements). Actuarial rates of freedom from complications were: valve thrombosis 100%, embolism 92 +/- 2.8%, and anticoagulant-related bleeding 77 +/- 5.6%. The linearized rates per 100 pt-yr were: embolism 0.89 (aortic 0.74, mitral 1.30); anticoagulant-related bleeding 2.56; paravalvular leakage overall 0.20 (aortic 0.37); prosthetic valve endocarditis overall 0.20 (aortic 0.37). There was no hemolysis, prosthetic valve dysfunction or structural deterioration.

CONCLUSION

Over a 12-year time frame, the CarboMedics prosthetic heart valve has proven to be a highly reliable device with no structural failures, and a low incidence of valve-related complications.

Seven-and-a-half years clinical experience with the CarboMedics prosthetic heart valve

Seven and a half year clinical experience with the CarboMedics prosthetic heart valve is presented. A total of 287 valves were inserted in 277 patients. The first 132 patients were followed in a prospective, and the remaining 145 patients in a partly prospective and partly retrospective manner. The follow up was 98.9% complete with a total of 1,055 patient-years. Actuarial survival at 7.5 years was 74.0% +/- 3.5% overall; 76.0% +/- 4.3% for single aortic, 75.0% +/- 6.5% for single mitral and 76.0% +/- 11.4% for double valve replacements. The actuarial rates of freedom from complications were as follows: valve thrombosis 99.6% +/- 0.4%, embolism 96.0% +/- 1.7%, and anticoagulant-related bleeding 88.0% +/- 2.4%. There was no hemolysis, prosthetic valve dysfunction, or structural deterioration. The linearized rates per 100 patients-years were as follows: valve thrombosis 0.09 (mitral 0.30); embolism 0.75 (aortic 0.31, mitral 1.80); anticoagulant related bleeding 2.84; paravalvular leakage overall 0.19 (aortic 0.31); prosthetic valve endocarditis 0.19 (aortic 0.31). Over a 7.5-year time frame, the CarboMedics prosthetic heart valve has been highly reliable with a low incidence of valve related complications.