K. J. Mikines

Insulin-Stimulated Muscle Glucose Clearance in Patients With NIDDM: Effects of One-Legged Physical Training

Physical training increases insulin action in skeletal muscle in healthy men. In non-insulin-dependent diabetes mellitus (NIDDM), only minor improvements in whole-body insulin action are seen. We studied the effect of training on insulin-mediated glucose clearance rates (GCRs) in the whole body and in leg muscle in seven patients with NIDDM and in eight healthy control subjects. One-legged training was performed for 10 weeks. GCR in whole body and in both legs were measured before, the day after, and 6 days after training by hyperinsulinemic (28, 88, and 480 mU · min−1 · m−2), isoglycemic clamps combined with the leg balance technique. On the 5th day of detraining, one bout of exercise was performed with the nontraining leg. Muscle biopsies were obtained before and after training. Whole-body GCRs were always lower (P < 0.05) in NIDDM patients compared with control subjects and increased (P < 0.05) in response to training. In untrained muscle, GCR was lower (P < 0.05) in NIDDM patients (13 ± 4, 91 ± 9, and 148 ± 12 ml/min) compared with control subjects (56 ± 12, 126 ± 14, and 180 ± 14 ml/min). It Increased (P < 0.05) in both groups in response to training (43 ± 10, 144 ± 17, and 205 ± 24 [NIDDM patients] and 84 ± 10, 212 ± 20, and 249 ± 16 ml/min [control subjects]). Acute exercise did not increase leg GCR. In NIDDM patients, the effect of training was lost after 6 days, while the effect lasted longer in control subjects. Training increased (P < 0.05) muscle lactate production and glucose storage as well as glycogen synthase (GS) mRNA in both groups. We conclude that training increases insulin action in skeletal muscle in control subjects and NIDDM patients, and in NIDDM patients normal values may be obtained. The increase in trained muscle cannot fully account for the increase in whole-body GCR. Improvements in GCR involve enhancement of insulin-mediated increase in muscle blood flow and the ability to extract glucose. They are accompanied by enhanced nonoxidative glucose disposal and increases in GS mRNA. The improvements in insulin action are short-lived.

Physical Training Increases Muscle GLUT4 Protein and mRNA in Patients With NIDDM

Patients with non-insulin-dependent diabetes mellitus (NIDDM) exhibit insulin resistance and decreased glucose transport in skeletal muscle. Total content of muscle GLUT4 protein is not affected by NIDDM, whereas GLUT4 mRNA content is reported, variously, to be unaffected or increased. Physical training is recommended in the treatment of NIDDM, but the effect of training on muscle GLUT4 protein and mRNA content is unknown. To clarify the effect of training in NIDDM, seven men with NIDDM (58 ± 2 years of age [mean ± SE]) and eight healthy men (59 ± 1 years of age) (control group) performed one-legged ergometer bicycle training for 9 weeks, 6 days/week, 30 min/day. Biopsies were obtained from the vastus lateralis leg muscle before and after training. GLUT4 protein analyses was performed along with analyses of muscle biopsies from five young (23 ± 1 years of age) (young group), healthy subjects who participated in a previously published identical study. In response to training, maximal oxygen uptake increased (Δ 3.3 ± 1.8 in NIDDM subjects and 4.5 ± 1.2 ml.min−1·kg−1 in control subjects [both P < 0.05]). Before training, GLUT4 protein content was similar in NIDDM, control, and young subjects (0.35 ± 0.02, 0.34 ± 0.03, and 0.41 ± 0.03 arbitrary units, respectively), and it increased (P < 0.05) in all groups during training (to 0.43 ± 0.03, 0.40 ± 0.03, and 0.57 ± 0.08 arbitrary units, respectively). GLUT4 mRNA content was always lower in NIDDM compared with control subjects (P < 0.05) and increased in both groups (P < 0.05) during training (94 ± 6 to 122 ± 8 and 151 ± 5 to 170 ± 4 arbitrary units/10 μg total RNA, respectively). We conclude that muscle GLUT4 protein and mRNA increase in both NIDDM and control subjects in response to training. GLUT4 mRNA content is lower in NIDDM subjects compared with control subjects. GLUT4 protein content does not change with age.

Effects of insulin and exercise on muscle lipoprotein lipase activity in man and its relation to insulin action.

The effects of exercise and a physiological increase in plasma insulin concentration on muscle lipoprotein lipase activity (mLPLA), leg exchange of glucose, and serum lipoprotein levels were investigated in healthy young men. During euglycemic hyperinsulinemia (n = 7) at 44 mU.liter-1, m-LPLA in non-exercised muscle decreased from 30 +/- 7.4 mU.g-1 wet weight (w.w.) (mean +/- SE) to 19 +/- 3.3 (P less than 0.05). Furthermore, the decrease in m-LPLA correlated closely (r = 0.97, P less than 0.05) with the increase in leg glucose uptake. Moreover, basal m-LPLA correlated with the insulin-induced increase in leg glucose uptake (r = 0.93, P less than 0.05). In the control group (n = 6) in which saline was infused in place of insulin and glucose, m-LPLA in nonexercised muscle did not change with time. No change in m-LPLA was observed immediately after one-legged knee extension exercise, but 4 h after exercise m-LPLA was higher (P less than 0.05) in the exercised thigh (47 +/- 17.8 mU.g-1 w.w.) compared with the contralateral nonexercised thigh (29 +/- 6.3 mU.g-1 w.w.). This difference was not found 8 h after exercise. The triacylglycerol content of serum lipoproteins decreased during insulin infusion. It is concluded that in contrast to the effect on adipose tissue, physiological concentrations of insulin decrease m-LPLA in proportion to the effect of insulin on muscle glucose uptake, while muscle contractions cause a local, delayed, and transient increase in m-LPLA. Further-more, basal m-LPLA is an indicator of muscle insulin sensitivity.

GLUT 4 and insulin receptor binding and kinase activity in trained human muscle.

1. Physical training enhances sensitivity and responsiveness of insulin‐mediated glucose uptake in human muscle. This study examines if this effect of physical training is due to increased insulin receptor function or increased total concentration of insulin‐recruitable glucose transporter protein (GLUT 4). 2. Seven healthy young subjects carried out single leg bicycle training for 10 weeks at 70% of one leg maximal oxygen uptake (VO2,max). Subsequently biopsies were taken from the vastus lateralis muscle of both legs. 3. Single leg VO2,max increased for the trained leg (46 +/‐ 3 to 52 +/‐ 2 ml min‐1 kg‐1 (means +/‐ S.E.M., P < 0.05), and cytochrome c oxidase activity was higher in this compared to the untrained leg (2.0 +/‐ 0.1 vs. 1.4 +/‐ 0.1 nmol s‐1 (mg muscle)‐1, P < 0.05). Insulin binding as well as basal‐ and insulin‐stimulated receptor kinase activity did not differ between trained and untrained muscle. The concentration of GLUT 4 protein was higher in the former (14.9 +/‐ 1.9 vs. 11.6 +/‐ 1.0 arbitrary units (micrograms protein)‐1 in crude membranes, P < 0.05). The training‐induced increase in GLUT 4 (26 +/‐ 11%) matched a previously reported increase in maximum insulin‐stimulated leg glucose uptake (25 +/‐ 7%) in the same subjects, and individual values of the two variables correlated (correlation coefficient (r) = 0.84, P < 0.05). 4. In conclusion, in human muscle training induces a local contraction‐dependent increase in GLUT 4 protein, which enhances the effect of insulin on glucose uptake. On the other hand, insulin receptor function in muscle is unlikely to be affected by training.

Normal Effect of Insulin to Stimulate Leg Blood Flow in NIDDM

In patients with non-insulin-dependent diabetes mellitus (NIDDM), a decreased effect of insulin in stimulating leg blood flow (LBF) has been reported. We reinvestigated the effect of insulin on LBF and validated our data by use of other measures. Eight healthy men (control group) and seven men with NIDDM were studied (age 59 ± 1 and 58 ± 3 years, weight 83 ± 3 and 86 ± 6 kg, fat-free mass 66 ± 1 and 64 ± 3 kg, respectively [mean ± SE, all P > 0.05]; body mass index 26 ± 1 and 29 ± 1 kg/m2, fasting plasma insulin 72 ± 7 and 187 ± 22 pmol/l, fasting plasma glucose 5.8 ± 0.2 and 10.2 ± 1.7 mmoM [all P < 0.05]). A three-step hyperinsulinemic glucose clamp (ambient glucose level) was performed, combined with catheterization of an artery and both femoral veins. Expiratory air was collected, LBF was measured by thermodilution, and blood was sampled and analyzed for oxygen content. Insulin concentration was increased to 416 ± 22 and 509 ± 43 (step I), 1,170 ± 79 and 1,299 ± 122 (step II), and 15,936 ± 1,126 and 16,524 ± 1,916 (step III) pmol/l in control and NIDDM subjects, respectively (P > 0.05). LBF increased similarly (P > 0.05) in the two groups (from 287 ± 23 and 302 ± 12 [basal] to 308 ± 31 and 362 ± 9 [I], 371 ± 29 and 409 ± 17 [II], and 434 ± 32 and 472 ± 29 [III] ml min−1 leg−1 in control and NIDDM subjects, respectively). Leg oxygen uptake always increased in the face of constant venous Po2 (JP > 0.05; 4.3 ± 0.2 and 4.5 ± 0.2 [basal], 4.3 ± 0.2 and 4.6 ± 0.2 [I], 4.8 ± 0.2 and 4.6 ± 0.2 [II], and 4.7 ± 0.1 and 4.4 ± 0.2 [III] kPa in control and NIDDM subjects, respectively). Both leg and whole body O2 uptake increased similarly in the two groups. In conclusion, at ambient glucose levels, the effect of insulin in stimulating LBF is normal in NIDDM. Moreover, insulin-mediated vasodilation is closely linked to muscle metabolic rate.

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°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 (GMOSD) and uncoupled respiration were significantly (P < 0.05) higher in visceral (0.95 ± 0.05 and 1.15 ± 0.06 pmol O2 s−1 mg−1, respectively) compared with subcutaneous (0.76 ± 0.04 and 0.98 ± 0.05 pmol O2 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.

Early experience with multiparametric magnetic resonance imaging-targeted biopsies under visual transrectal ultrasound guidance in patients suspicious for prostate cancer undergoing repeated biopsy

Abstract Objectives. The purpose of this study was to investigate the detection rate of prostate cancer (PCa) by multiparametric magnetic resonance imaging-targeted biopsies (mp-MRI-bx) in patients with prior negative transrectal ultrasound biopsy (TRUS-bx) sessions without previous experience of this. Material and methods. Eighty-three patients with prior negative TRUS-bx scheduled for repeated biopsies due to persistent suspicion of PCa were prospectively enrolled. mp-MRI was performed before biopsy and all lesions were scored according to the Prostate Imaging Reporting and Data System (PI-RADS) and Likert classification. All underwent repeated TRUS-bx (10 cores) and mp-MRI-bx under visual TRUS guidance of any mp-MRI-suspicious lesion not targeted by systematic TRUS-bx. Results.PCa was found in 39 out of 83 patients (47%) and mp-MRI identified at least one lesion with some degree of suspicion in all 39 patients. Both PI-RADS and Likert scoring showed a high correlation between suspicion of malignancy and biopsy results (p < 0.0001). Five patients (13%) had cancer detected only on mp-MRI-bx outside the TRUS-bx areas (p = 0.025) and another seven patients (21%) had an overall Gleason score upgrade of at least one grade based on the mp-MRI-bx. Secondary PCa lesions not visible on mp-MRI were detected by TRUS-bx in six out of 39 PCa patients. The secondary foci were all Gleason 6 (3 + 3) in 5–10% of the biopsy core. According to the Epstein criteria, 37 out of 39 cancer patients were classified as clinically significant. Conclusion. Using mp-MRI, even without previous experience, can improve the detection rate of significant PCa at repeated biopsy and allows more accurate Gleason grading.

Muscle and liver glycogen, protein, and triglyceride in the rat: Effect of exercise and of the sympatho-adrenal system

SummaryWe have previously found that during exercise net muscle glycogen breakdown is impaired in adrenodemedullated rats, as compared with controls. The present study was carried out to elucidate whether, in rats with deficiencies of the sympatho-adrenal system, diminished exercise-induced glycogenolysis in skeletal muscle was accompanied by increased breakdown of triglyceride and/or protein. Thus, the effect of exhausting swimming and of running on concentrations of glycogen, protein, and triglyceride in skeletal muscle and liver were studied in rats with and without deficiencies of the sympatho-adrenal system. In control rats, both swimming and running decreased the concentration of glycogen in fast-twitch red and slow-twitch red muscle whereas concentrations of protein and triglyceride did not decrease. In the liver, swimming depleted glycogen stores but protein and triglyceride concentrations did not decrease. In exercising rats, muscle glycogen breakdown was impaired by adrenodemedullation and restored by infusion of epinephrine. However, impaired glycogen breakdown during exercise was not accompanied by a significant net breakdown of protein or triglyceride. Surgical sympathectomy of the muscles did not influence muscle substrate concentrations. The results indicate that when glycogenolysis in exercising muscle is impeded by adrenodemedullation no compensatory increase in breakdown of triglyceride and protein in muscle or liver takes place. Thus, indirect evidence suggests that, in exercising adrenodemedullated rats, fatty acids from adipose tissue were burnt instead of muscle glycogen.

Endurance training improves insulin sensitivity and body composition in prostate cancer patients treated with androgen deprivation therapy

Insulin resistance and changes in body composition are side effects of androgen deprivation therapy (ADT) given to prostate cancer patients. The present study investigated whether endurance training improves insulin sensitivity and body composition in ADT-treated prostate cancer patients. Nine men undergoing ADT for prostate cancer and ten healthy men with normal testosterone levels underwent 12 weeks of endurance training. Primary endpoints were insulin sensitivity (euglycemic-hyperinsulinemic clamps with concomitant glucose-tracer infusion) and body composition (dual-energy X-ray absorptiometry and magnetic resonance imaging). The secondary endpoint was systemic inflammation. Statistical analysis was carried out using two-way ANOVA. Endurance training increased VO2max (ml(O2)/min per kg) by 11 and 13% in the patients and controls respectively (P<0.0001). The patients and controls demonstrated an increase in peripheral tissue insulin sensitivity of 14 and 11% respectively (P<0.05), with no effect on hepatic insulin sensitivity (P=0.32). Muscle protein content of GLUT4 (SLC2A4) and total AKT (AKT1) was also increased in response to the training (P<0.05 and P<0.01 respectively). Body weight (P<0.0001) and whole-body fat mass (FM) (P<0.01) were reduced, while lean body mass (P=0.99) was unchanged. Additionally, reductions were observed in abdominal (P<0.01), subcutaneous (P<0.05), and visceral (P<0.01) FM amounts. The concentrations of plasma markers of systemic inflammation were unchanged in response to the training. No group × time interactions were observed, except for thigh intermuscular adipose tissue (IMAT) (P=0.01), reflecting a significant reduction in the amount of IMAT in the controls (P<0.05) not observed in the patients (P=0.64). In response to endurance training, ADT-treated prostate cancer patients exhibited improved insulin sensitivity and body composition to a similar degree as eugonadal men.

Elimination of Ascorbic Acid After High-Dose Infusion in Prostate Cancer Patients: A Pharmacokinetic Evaluation

Treatment with high‐dose intravenous (IV) ascorbic acid (AA) is used in complementary and alternative medicine for various conditions including cancer. Cytotoxicity to cancer cell lines has been observed with millimolar concentrations of AA. Little is known about the pharmacokinetics of high‐dose IV AA. The purpose of this study was to assess the basic kinetic variables in human beings over a relevant AA dosing interval for proper design of future clinical trials. Ten patients with metastatic prostate cancer were treated for 4 weeks with fixed AA doses of 5, 30 and 60 g. AA was measured consecutively in plasma and indicated first‐order elimination kinetics throughout the dosing range with supra‐physiological concentrations. The target dose of 60 g AA IV produced a peak plasma AA concentration of 20.3 mM. Elimination half‐life was 1.87 hr (mean, S.D. ± 0.40), volume of distribution 0.19 L/kg (S.D. ±0.05) and clearance rate 6.02 L/hr (100 mL/min). No differences in pharmacokinetic parameters were observed between weeks/doses. A relatively fast first‐order elimination with half‐life of about 2 hr makes it impossible to maintain AA concentrations in the potential cytotoxic range after infusion stop in prostate cancer patients with normal kidney function. We propose a regimen with a bolus loading followed by a maintenance infusion based on the calculated clearance.