Androgen receptors and testosterone in men--effects of protein ingestion, resistance exercise and fiber type

The purpose of this study was to examine the impact of protein ingestion on circulating testosterone and muscle androgen receptor (AR) as well as on insulin-like growth factor-I (MGF and IGF-IEa) responses to a resistance exercise (RE) bout in (57-72 year) men. Protein (15 g whey) (n=9) or placebo (n=9) was consumed before and after a RE bout (5 sets of 10 repetition maximums), and vastus lateralis muscle biopsies were taken pre, 1 and 48 h post-RE. The protein ingestion blunted the RE-induced increase in serum free and total testosterone while the RE bout significantly increased muscle AR mRNA levels in older men (P<0.05). However, protein ingestion did not significantly affect AR mRNA or protein expression, or MGF and IGF-IEa mRNA expression at 1 and 48 h post-RE. Immunohistochemical staining of muscle cross-sections was done with antibodies specific to AR and MyHC I and II and showed that there seems to be within or near the type-I muscle fibers a greater staining of ARs than within or near the type-II fibres. In conclusion, the protein ingestion hinders RE-induced increase in serum testosterone in older men but may not significantly affect muscle AR, MGF or IGF-IEa gene expression. Furthermore, the present study shows that even older men are able to increase muscle AR mRNA expression in response to a RE bout.     

Acute and long-term effects of resistance exercise with or without protein ingestion on muscle hypertrophy and gene expression

The effects of timed ingestion of high-quality protein before and after resistance exercise are not well known. In this study, young men were randomized to protein (n = 11), placebo (n = 10) and control (n = 10) groups. Muscle cross-sectional area by MRI and muscle forces were analyzed before and after 21 weeks of either heavy resistance training (RT) or control period. Muscle biopsies were taken before, and 1 and 48 h after 5 × 10 repetition leg press exercise (RE) as well as 21 weeks after RT. Protein (15 g of whey both before and after exercise) or non-energetic placebo were provided to subjects in the context of both single RE bout (acute responses) as well as each RE workout twice a week throughout the 21-week-RT. Protein intake increased (P ≤ 0.05) RT-induced muscle cross-sectional area enlargement and cell-cycle kinase cdk2 mRNA expression in the vastus lateralis muscle suggesting higher proliferating cell activation response with protein supplementation. Moreover, protein intake seemed to prevent 1 h post-RE decrease in myostatin and myogenin mRNA expression but did not affect activin receptor IIb, p21, FLRG, MAFbx or MyoD expression. In conclusion, protein intake close to resistance exercise workout may alter mRNA expression in a manner advantageous for muscle hypertrophy.     

Effect of hen's egg yolk on capacitation and acrosome reaction of diluted canine spermatozoa

The aim of this study was to investigate the influence of progesterone, cholesterol and calcium (Ca²⁺) in an egg-yolk-containing extender on capacitation and acrosome reactions (AR) of diluted canine spermatozoa during 4 days of cooled-storage. For this purpose, we first investigated the effect of supplementation of a Tris–citrate–fructose buffer (TCF) with progesterone in a final concentration of 0.1, 0.2 and 1.0 μg progesterone/ml TCF-diluted semen. We then compared the effects of TCF and the same buffer-containing 20% egg yolk (TCF–EY). In egg yolks and the TCF–EY, progesterone was measured by enzyme immunoassay, cholesterol by enzymatic colorimetry and Ca²⁺ by flame atomic absorption spectrophotometry. For both experiments, ejaculates from eight dogs were used. For the comparison of diluents, one ejaculate was divided and one half diluted with TCF, the other with TCF–EY. One half of each TCF- and TCF–EY-diluted sample was evaluated immediately (D1), the other after storage for 4 days at +4 °C (D4). In diluted semen, motility and viability were measured by a computer assisted sperm analyzer (CASA; Sperm Vision, Minitüb, Germany), capacitation and AR were evaluated with a modified chlortetracycline assay (CTC) and the AR additionally by flow cytometry. Results: Supplementation of progesterone revealed, that between D1 and D4, total and progressive motility decreased with all progesterone concentrations, while viability as well as percentage of capacitated and acrosome reacted spermatozoa stayed constant. Progesterone-, cholesterol- and Ca²⁺ concentrations in egg yolks were 524.8 ± 131.4 ng/g, 13.9 ± 2.03 mg/g and 1.27 ± 0.17 mg/g, respectively. In the TCF–EY-diluent, the respective values were 210.9 ng/g, 2.52 mg/g and 1.1 mg/g. In TCF–semen, at D1, motility and viability were significantly higher than in TCF–EY-samples (p < 0.05), however at D4, no significant differences were detectable. Further, in TCF–semen, percentages of spermatozoa with intact membranes decreased significantly (p < 0.05) and capacitated spermatozoa increased (p < 0.05), which was not seen in TCF–EY-samples. In all samples, low percentages of AR were detected and after 4 days, the highest value of AR in TCF–EY-samples was 5.3% on average, as detected by flow cytometry. We therefore conclude that progesterone from egg yolk in routine extenders does not substantially influence semen longevity or AR of canine semen during cold-storage for 4 days. In contrary, egg yolk seems to prevent a significant increase in capacitated spermatozoa.     

Beneficial effects of resistance exercise on glycemic control are not further improved by protein ingestion

Purpose

To investigate the mechanisms underpinning modifications in glucose homeostasis and insulin sensitivity 24 h after a bout of resistance exercise (RE) with or without protein ingestion.

Methods

Twenty-four healthy males were assigned to a control (CON; n = 8), exercise (EX; n = 8) or exercise plus protein condition (EX+PRO; n = 8). Muscle biopsy and blood samples were obtained at rest for all groups and immediately post-RE (75% 1RM, 8×10 repetitions of leg-press and extension exercise) for EX and EX+PRO only. At 24 h post-RE (or post-resting biopsy for CON), a further muscle biopsy was obtained. Participants then consumed an oral glucose load (OGTT) containing 2 g of [U-¹³C] glucose during an infusion of 6, 6-[²H₂] glucose. Blood samples were obtained every 10 min for 2 h to determine glucose kinetics. EX+PRO ingested an additional 25 g of intact whey protein with the OGTT. A final biopsy sample was obtained at the end of the OGTT.

Results

Fasted plasma glucose and insulin were similar for all groups and were not different immediately post- and 24 h post-RE. Following RE, muscle glycogen was 26±8 and 19±6% lower in EX and EX+PRO, respectively. During OGTT, plasma glucose AUC was lower for EX and EX+PRO (75.1±2.7 and 75.3±2.8 mmol·L⁻¹∶120 min, respectively) compared with CON (90.6±4.1 mmol·L⁻¹∶120 min). Plasma insulin response was 13±2 and 21±4% lower for EX and CON, respectively, compared with EX+PRO. Glucose disappearance from the circulation was ∼12% greater in EX and EX+PRO compared with CON. Basal 24 h post-RE and insulin-stimulated PAS-AS160/TBC1D4 phosphorylation was greater for EX and EX+PRO.

Conclusions

Prior RE improves glycemic control and insulin sensitivity through an increase in the rate at which glucose is disposed from the circulation. However, co-ingesting protein during a high-glucose load does not augment this response at 24 h post-exercise in healthy, insulin-sensitive individuals.     

In vitro biohydrogenation of four dietary fats

This study was designed to determine in vitro rates of biohydrogenation of dietary unsaturated fatty acids by a mixed population of rumen microbes. The four dietary fats [Alifet High-Energy^® (AHE), Alifet-Repro^® (AR), Megalac^® (MG), and Energy Booster^® (EB)] differ in method of preparation, fatty acid composition, or both of these factors. Dietary fats (20 mg) were incubated with 4 mL strained rumen fluid diluted with 16 mL of medium, 0.8 mL of reducing solution buffer, and 200 mg of a synthetic diet (370 g cellulose, 370 g starch, and 160 g casein per kg DM) at 37 °C. Total contents were collected after 0, 6, 12, 24, or 36 h and change in fatty acid content determined. Disappearance of oleic acid was minimal (0.05–0.20) in AR and MG but moderate (about 0.60) in AHE and EB after 36 h of incubation. Rate of biohydrogenation of linoleic and linolenic acids from AR were similar (0.025 ± 0.009 h⁻¹) and 0.65 of these fatty acids remained intact after 36 h. Rate of biohydrogenation of linoleic acid was four times greater than for oleic acid (0.040 ± 0.013 h⁻¹ versus 0.009 ± 0.002 h⁻¹) in MG. Thus, 0.65 of the linoleic acid but only 0.20 of the oleic acid had disappeared from MG after 36 h. Trans-11 and trans-12 were the predominant trans-isomers in AHE and AR cultures whereas trans-9 and trans-10 were the predominant trans-isomers in EB and MG cultures. None of the dietary fats contained conjugated linoleic acid (CLA) but CLA was present in the incubation inoculum. The amount of CLA decreased with time but this was not affected by source of dietary fat. Most (0.90–0.95) of the long-chain fatty acids eicosapentaenoic (EPA) and docosahexaenoic (DHA) in AR remained after 36 h of incubation. Results demonstrate that biohydrogenation varied among fatty acids and among source of dietary fat and indicate that AR can be used to increase post-ruminal supply of linolenic, EPA and DHA.     

Effect of resistance exercise on muscle steroid receptor protein content in strength-trained men and women

The purpose of this study was to examine the acute effect of resistance exercise (RE) on muscle androgen receptor (AR) and glucocorticoid receptor (GR) protein content. Fifteen resistance-trained men (n = 8; 21 ± 1 years, 175.3 ± 6.7 cm, 90.8 ± 11.6 kg) and women (n = 7; 24 ± 5 years, 164.6 ± 6.7 cm, 76.4 ± 15.6 kg) completed 6 sets of 10 repetitions of heavy squats. Blood samples were obtained before RE, after 3 and 6 sets of squats, and 5, 15, 30 and 70 min after RE. Muscle biopsies from the vastus lateralis were obtained before RE, and 10 min and 70 min after RE. Blood samples were analyzed for total and free testosterone concentrations and muscle samples were analyzed for AR and GR protein content. Circulating total testosterone increased significantly (p ≤ 0.05) in men and free testosterone increased in men and women with exercise. AR was significantly reduced at 70 min post-exercise in men and at 10 min post-exercise in women compared to pre-exercise. There were no changes in GR following RE, but GR was significantly higher in women compared to men. These findings support a current paradigm for stabilization followed by a reduction and then a rebound in the acute AR response to RE but demonstrate that gender differences exist in the timeline of the AR response.     

Proteolytic mRNA expression in response to acute resistance exercise in human single skeletal muscle fibers.

The purpose of this study was to characterize changes in mRNA expression of select proteolytic markers in human slow-twitch [myosin heavy chain (MHC) I] and fast-twitch (MHC IIa) single skeletal muscle fibers following a bout of resistance exercise (RE). Muscle biopsies were obtained from the vastus lateralis of eight young healthy sedentary men [23 +/- 2 yr (mean +/- SD), 93 +/- 17 kg, 183 +/- 6 cm] before and 4 and 24 h after 3 x 10 repetitions of bilateral knee extensions at 65% of one repetition maximum. The mRNA levels of TNF-alpha, calpains 1 and 2, muscle RING (really interesting novel gene) finger-1 (MuRF-1), atrogin-1, caspase-3, B-cell leukemia/lymphoma (Bcl)-2, and Bcl-2-associated X protein (Bax) were quantified using real-time RT-PCR. Generally, MHC I fibers had higher (1.6- to 5.0-fold, P < 0.05) mRNA expression pre- and post-RE. One exception was a higher (1.6- to 3.9-fold, P < 0.05) Bax-to-Bcl-2 mRNA ratio in MHC IIa fibers pre- and post-RE. RE increased (1.4- to 4.8-fold, P < 0.05) MuRF-1 and caspase-3 mRNA levels 4-24 h post-RE in both fiber types, whereas Bax-to-Bcl-2 mRNA ratio increased 2.2-fold (P < 0.05) at 4 h post-RE only in MHC I fibers. These results suggest that MHC I fibers have a greater proteolytic mRNA expression pre- and post-RE compared with MHC IIa fibers. The greatest mRNA induction following RE was in MuRF-1 and caspase-3 in both fiber types. This altered and specific proteolytic mRNA expression among slow- and fast-twitch muscle fibers indicates that the ubiquitin/proteasomal and caspase pathways may play an important role in muscle remodeling with RE.     

Effect of magnesium supplementation and training on magnesium tissue distribution in rats

The aim of this work is to study the effect of training and Mg supplementation on body pools of Mg and on Mg tissue distribution. Forty male Wistar rats were divided into four groups (n=10): control group (C); trained group (T); Mg-supplemented group (+Mg); and trained and Mg-supplemented group (+MgT). The Mg supplement (100 ppm of Mg) was given in the drinking water for 21 d. The training consisted of swimming during 60% of maximal swimming time obtained in the first session to exhaustion, during 3 wk (5 d a week). The variables measured were: erythrocytes (RBC), hemoglobin (Hb), hematocrit (Hto), total proteins (TP), and Mg in serum, RBC, liver, muscle, bone, and kidney. There was less Mg in liver, muscle, and erythrocyte in trained animals than in control or supplemented animals (T vs C, +MgT vs C and +MgT vs +Mg) (p < 0.01). Trained antimals (T and +MgT) showed higher Mg kidney rates than the untrained ones (p<0.01). There was less bone Mg in control (C) and in supplemented and trained (+MgT) groups than in trained (T) and in supplemented (+Mg) animals (p<0.01). Serum Mg showed a decreasing concentration profile in the following order: +Mg, +MgT, T, C (p<0.01). We conclude that Mg supplementation improves bone and serum Mg levels, but this does not affect Mg status in soft tissues. Maintained exercise leads to a diminution of Mg in the aforementioned soft tissues that is not noticeable in serum, probably provoked by an increase of renal excretion.     

Differences in motor unit behavior during isometric contractions in patients with diabetic peripheral neuropathy at various disease severities

The aim of this study was to determine whether HD-sEMG is sensitive to detecting changes in motor unit behavior amongst healthy adults and type 2 diabetes mellitus (T2DM) patients presenting diabetic peripheral neuropathy (DPN) at different levels. Healthy control subjects (CON, n = 8) and T2DM patients presenting no DPN symptoms (ABS, n = 8), moderate DPN (MOD, n = 18), and severe DPN (SEV, n = 12) performed isometric ankle dorsiflexion at 30 % maximum voluntary contraction while high-density surface EMG (HD-sEMG) was recorded from the tibialis anterior muscle. HD-sEMG signals were decomposed, providing estimates of discharge rate, motor unit conduction velocity (MUCV), and motor unit territory area (MUTA). As a result, the ABS group presented reduced MUCV compared to CON. The groups with diabetes presented significantly larger MUTA compared to the CON group (p < 0.01), and the SEV group presented a significantly lower discharge rate compared to CON and ABS (p < 0.01). In addition, the SEV group presented significantly higher CoV_force compared to CON and MOD. These results support the use of HD-SEMG as a method to detect peripheral and central changes related to DPN.     

Induction and removal of DNA damage in blood leukocytes of patients with type 2 diabetes mellitus undergoing hemodialysis

Type 2 diabetes mellitus (T2DM) is associated with a high production of reactive oxygen species, which may cause oxidative DNA damage. High levels of genomic damage have been associated with renal failure and hemodialysis. However, no information is available in the literature concerning the levels of DNA damage in T2DM individuals who are dependent on hemodialysis. This study used the comet assay to assess the levels of DNA damage before, immediately after and 48 h after the hemodialysis session in 25 patients with T2DM and in a group of 20 healthy individuals, selected according to mean age, sex and smoking habit. Our results showed increased levels of DNA damage in hemodialysis-dependent T2DM individuals (12.36 ± 8.04) when compared with healthy individuals (7.35 ± 7.41) (p = 0.014). Damage levels increased immediately after the hemodialysis session (19.76 ± 12.40) (p = 0.04), which suggests a possible action of pro-oxidative factors related to the therapy, with a genotoxic effect on cells. Results obtained 48 h after hemodialysis (6.44 ± 5.99) evidenced damage removal (p = 0.001), which may be suggestive of DNA repair.     

Increased circulating IL-8 is associated with reduced IGF-1 and related to poor metabolic control in adolescents with type 1 diabetes mellitus

Background: A dysregulated growth hormone (GH)/insulin-like growth factor 1 (IGF-1) axis is well-recognized in children and adolescents with type 1 diabetes mellitus (T1DM). Decreased IGF-1 levels can also be found in chronic inflammatory diseases, while hyperglycemia promotes inflammatory cytokine production. Therefore, inflammatory cytokines may link poor metabolic control with GH/IGF-1 axis changes. This study examined the relationship between serum inflammatory cytokines and IGF-1 in adolescents (age 13–18) with TIDM in chronic poor (n = 17) or favorable (n = 19) glucose control. Poor control (PC) was defined as 3, consistent HbA1C > 9% during the previous 2 years, while favorable control (FC) was consistent levels of HbA1C < 9%. Results: HbA1C (FC: 7.5 ± 0.6%; PC: 10.5 ± 0.9%, p < 0.001) and interleukin (IL)-8 (FC: 3.7 ± 4.0 pg/ml; PC: 7.4 ± 4.3 pg/ml, p = 0.01) were increased and IGF-1 (FC: 536.5 ± 164.3 ng/ml; PC: 408.9 ± 157.1 ng/ml, p = 0.03) was decreased in patients with poor control compared to patients with favorable control. Moreover, IL-8 was inversely correlated with IGF-1 (r = −0.40, p = 0.03) and positively correlated with HbA1C (r = 0.36, p = 0.03). Conclusions: In adolescents with T1DM and chronic, poor glucose control, increased serum IL-8 is associated with reduced IGF-1 suggesting a pro-inflammatory milieu that may contribute to alterations in the GH/IGF-1 axis.     

Force variability depends on core and muscle temperature

The aim of this study was to investigate if voluntary activation and force variability during maximal voluntary contraction (MVC) depends more on muscle (local) or body (core) temperature. Ten volunteers performed a 2-min MVC of the knee extensors under the control (CON) conditions (ambient temperature (21 °C), relative humidity (30%), and air velocity (∼0.1 m/s)) as well as after heating (HT) and cooling (CL) of the lower body. During water manipulation procedure lower body was immersed up to the waist in a water bath at ∼44 °C for 45 min for HT experiment, and ∼15 °C for 30 min for CL experiment. Peak torque, torque variability, muscle voluntary activation and half-relaxation time were assessed during the exercise. HT increased muscle (2.8±0.2 °C) and rectal (1.9±0.1 °C) temperatures while CL lowered muscle (2.2±0.2 °C) temperature, but did not affect rectal temperature. During 2-min MVC, peak torque decreased (P<0.05; SP>90%) and to a lower level in HT compared to CON and CL experiments (52.6±2.3% versus 69.0±2.3% and 65.6±1.9% MVC, respectively, P<0.05; SP>90%). Torque variability increased significantly during exercise and was significantly larger in HT and lower in CL compared to CON experiment. Voluntary activation of exercising muscle was more depressed in HT (i.e. greater central fatigue) and the smallest effect was found in CL compared to CON. In conclusion increased core and muscle temperature impairs voluntary activation and increases force variability of the exercising muscles while a local muscle cooling decrease force variability but has a small effect on central fatigue.     

Mechanical modulation of atrial flutter cycle length

Although atrial flutter (AFL) is considered a highly regular rhythm, small fluctuations in cycle length have been described. The mechanisms responsible for these interval oscillations have been investigated by recent studies in humans which have shown that cyclic variations in atrial volume and pressure following ventricular contraction may account for the spontaneous variability of AFL. Other studies have shown that variations in the dimensions of the atria, caused by hemodynamical alterations due to imposed manoeuvres, directly modify the rate of AFL. All this evidence has led to the development of the mechano-electrical feedback (MEF) hypothesis, which assumes that changes in atrial volume directly affect AFL cycle length variability by modifying the conduction properties of the circulating impulse in the atrium.In the present study, we re-examined the variability pattern of typical AFL by spectral analysis aiming to support the MEF hypothesis for AFL cycle length variability. In a study population of 30 patients with typical AFL, we observed that AFL cycle length presented a spontaneous beat-to-beat variability, composed of two oscillations: a main oscillation at the frequency of ventricular contraction (1.70±0.48 Hz, spectral power: 15.4±17.6 ms²) and a second oscillation at the frequency of respiration (0.32±0.07 Hz, spectral power: 2.9±2.6 ms²). Both ventricular and respiratory oscillations persisted after pharmacologic autonomic blockade (ventricular spectral power: 17.7±14.7 ms² (before block) vs 20.2±18.3 ms² (after block), p=NS; respiratory spectral power: 6.0±3.8 ms² (before block) vs 5.0±3.4 ms² (after block), p=NS), suggesting a non-neurally mediated underlying mechanism. Contrary to respiratory modulation of heart rate during sinus rhythm, respiratory AFL cycle length oscillations displayed a reverse pattern, with longer cycle lengths during inspiration and shorter during expiration (AA_insp=223.2±28.6 ms vs AA_exp=221.1±28.2 ms, p<0.0005), which was consistent with a mechanical modulation of AFL reentry.The use of spectral analysis techniques applied to ventricular interval series and combined with computer simulations of atrioventricular conduction showed that the respiratory oscillation of atrial cycle length determined an oscillation in ventricular intervals with longer intervals during inspiration and shorter during expiration (VV_insp=639.9±186.0 ms vs VV_exp=634.8±182.9 ms, p<0.05). Ventricular interval oscillations resulted amplified by a factor 1.8 with respect to corresponding atrial cycle length oscillations. Thus, the mechanical fluctuations in AFL cycle length, although of small amplitude, might become clinically relevant through a magnified effect on ventricular variability.     

The effect of the nitric oxide donor sodium nitroprusside on glucose uptake in human primary skeletal muscle cells

Nitric oxide (NO) has been implicated as an important signaling molecule in the insulin-independent, contraction-mediated glucose uptake pathway and may represent a novel strategy for blood glucose control in patients with type 2 diabetes (T2DM). The current study sought to determine whether the NO donor, sodium nitroprusside (SNP) increases glucose uptake in primary human skeletal muscle cells (HSkMC) derived from both healthy individuals and patients with T2DM. Vastus lateralis muscle cell cultures were derived from seven males with T2DM (aged 54 ± 2 years, BMI 31.7 ± 1.2 kg/m², fasting plasma glucose 9.52 ± 0.80 mmol/L) and eight healthy individuals (aged 46 ± 2 years, BMI 27.1 ± 1.5 kg/m², fasting plasma glucose 4.69 ± 0.12 mmol/L). Cultures were treated with both therapeutic (0.2 and 2 μM) and supratherapeutic (3, 10 and 30 mM) concentrations of SNP. An additional NO donor S-nitroso-N-acetyl-d,l-penicillamine (SNAP) was also examined at a concentration of 50 μM. Glucose uptake was significantly increased following both 30 and 60 min incubations with the supratherapeutic SNP treatments (P = 0.03) but not the therapeutic SNP doses (P = 0.60) or SNAP (P = 0.54). There was no difference in the response between the healthy and T2DM cell lines with any treatment or dose. The current study demonstrates that glucose uptake is elevated by supratherapeutic, but not therapeutic doses of SNP in human primary skeletal muscle cells derived from both healthy volunteers and patients with T2D. These data confirm that nitric oxide donors have potential therapeutic utility to increase glucose uptake in humans, but that SNP only achieves this in supratherapeutic doses. Further study to delineate mechanisms and the therapeutic window is warranted.     

Glucagon-like peptide-1 protects mesenteric endothelium from injury during inflammation

Glucagon-like peptide-1 (GLP-1) is a proglucagon-derived hormone with cellular protective actions. We hypothesized that GLP-1 would protect the endothelium from injury during inflammation. Our aims were to determine the: (1) effect of GLP-1 on basal microvascular permeability, (2) effect of GLP-1 on increased microvascular permeability induced by lipopolysaccaride (LPS), (3) involvement of the GLP-1 receptor in GLP-1 activity, and (4) involvement of the cAMP/PKA pathway in GLP-1 activity. Microvascular permeability (L_p) of rat mesenteric post-capillary venules was measured in vivo. First, the effect of GLP-1 on basal L_p was measured. Second, after systemic LPS injection, L_p was measured after subsequent perfusion with GLP-1. Thirdly, L_p was measured after LPS injection and perfusion with GLP-1 + GLP-1 receptor antagonist. Lastly, L_p was measured after LPS injection and perfusion with GLP-1 + inhibitors of the cAMP/PKA pathway. Results are presented as mean area under the curve (AUC) ± SEM. GLP-1 had no effect on L_p (AUC: baseline = 27 ± 1.4, GLP-1 = 1 ± 0.4, p = 0.08). LPS increased L_p two-fold (AUC: LPS = 54 ± 1.7, p < 0.0001). GLP-1 reduced the LPS increase in L_p by 75% (AUC: LPS + GLP-1 = 34 ± 1.5, p < 0.0001). GLP-1 antagonism reduced the effects of GLP-1 by 60% (AUC: LPS + GLP-1 + antagonist = 46 ± 2.0, p < 0.001). The cAMP synthesis inhibitor reduced the effects of GLP-1 by 60% (AUC: LPS + GLP-1 + cAMP inhibitor = 46 ± 1.5, p < 0.0001). The PKA inhibitor reduced the effects of GLP-1 by 100% (AUC: LPS + GLP-1 + PKA inhibitor = 56 ± 1.5, p < 0.0001). GLP-1 attenuates the increase in microvascular permeability induced by LPS. GLP-1 may protect the endothelium during inflammation, thus decreasing third-space fluid loss.     

Effects of sprint training on extrarenal potassium regulation with intense exercise in Type 1 diabetes.

Effects of sprint training on plasma K+ concentration ([K+]) regulation during intense exercise and on muscle Na+-K+-ATPase were investigated in subjects with Type 1 diabetes mellitus (T1D) under real-life conditions and in nondiabetic subjects (CON). Eight subjects with T1D and seven CON undertook 7 wk of sprint cycling training. Before training, subjects cycled to exhaustion at 130% peak O2 uptake. After training, identical work was performed. Arterialized venous blood was drawn at rest, during exercise, and at recovery and analyzed for plasma glucose, [K+], Na+ concentration ([Na+]), catecholamines, insulin, and glucagon. A vastus lateralis biopsy was obtained before and after training and assayed for Na+-K+-ATPase content ([3H]ouabain binding). Pretraining, Na+-K+-ATPase content and the rise in plasma [K+] ([K+]) during maximal exercise were similar in T1D and CON. However, after 60 min of recovery in T1D, plasma [K+], glucose, and glucagon/insulin were higher and plasma [Na+] was lower than in CON. Training increased Na+-K+-ATPase content and reduced [K+] in both groups (P < 0.05). These variables were correlated in CON (r = -0.65, P < 0.05) but not in T1D. This study showed first that mildly hypoinsulinemic subjects with T1D can safely undertake intense exercise with respect to K+ regulation; however, elevated [K+] will ensue in recovery unless insulin is administered. Second, sprint training improved K+ regulation during intense exercise in both T1D and CON groups; however, the lack of correlation between plasma delta[K+] and Na+-K+-ATPase content in T1D may indicate different relative contributions of K+-regulatory mechanisms.     

Skeletal muscle protein composition following 5 weeks of ULLS and resistance exercise countermeasures

The effects of 5 weeks of unilateral lower limb suspension (ULLS) and flywheel resistance exercise (RE) on skeletal muscle protein composition were examined in thirty-one subjects (40 +/- 8y), divided into three groups: ULLS, ULLS+RE, and RE. Pre and post biopsy samples were examined for protein concentration, myosin heavy chain (MHC) and actin concentration. VL protein concentration of the three groups did not change. Soleus protein concentration following ULLS decreased (p<0.05). MHC and actin content of the VL and soleus were unaltered. Muscle mass changed from pre to post: ULLS -11% (VL), -11% (soleus), both p<0.05; ULLS+RE +9%, p<0.05; RE +6%, P<0.05. Therefore, the increase or decrease in VL muscle mass over 5 weeks occurred while maintaining protein, MHC and actin. However, soleus muscle atrophy occurred at the expense of other muscle proteins, since MHC and actin were maintained and protein concentrations decreased.     

Growth and Solute Composition in Two Wheat Species Experiencing Combined Influence of Stress Conditions1

The effects of environmental stress combinations on the soluble metabolites were investigated in several cultivars of Triticum aestivum and T. durum. The seedlings grown at optimum (24/16°C), low (5/–5°C) (LT), and high (40/30°C) (HT) day/night temperature conditions were exposed to waterlogging, drought, and salinity (0.7% NaCl, w/w) stresses for six days. Root and shoot fresh weight significantly decreased under waterlogging, drought and salt stresses. Fresh weight was most reduced at severe drought + HT combinations. The lowest relative water content was found under drought stress + HT combination. Soluble carbohydrate (SC) contents increased under LT conditions, but decreased under HT conditions. Under HT + salt combinations, T. aestivum genotypes showed higher SC content thanT. durum genotypes. Proline content significantly increased in the case of water deficit and salt stress. Under drought and salt stresses, T. aestivum genotypes had lower proline contents than T. durum genotypes. These results indicate that biochemical responses to drought, waterlogging, and salt stresses were significantly changed in wheat seedlings under LT and HT conditions.