Migrations, admixture and genetic diversity in Central Argentinian Patagonia: analysis of autosomal Alu polymorphisms / Migraciones, mestizaje y diversidad genética en la Patagonia Central Argentina: análisis de polimorfismos autosómicos Alu

This study aimed to analyze autosomal Alu insertions in three localities from Patagonia Argentina belonging to the Andes region and the coast of the Chubut province. Knowledge of the genetic diversity of these populations, along with the genealogical data, will contribute to better understand historical information, differential migration process and bio-demographic composition of the Central Patagonia region. In order to achieve this objective, 16 autosomal Alu insertion polymorphisms were genotyped: ACE, APO-A1, TPA25, FXIIIB, A25, HS4.32, D1, HS4.69, HS2.43, Sb19.12, Yb8NBC120, Sb19.3, Yb8NBC125, Ya5NBC221, DM, and CD4. Our results showed that the Central Patagonia region presents a complex continental genetic admixture with marked Native American roots (39% ± 1.2), Eurasian (56% ± 1.73) and, to a lesser extent, African (5% ± 1.7). The genetic proximity of the Patagonian samples in relation to groups from Europe and Northern Africa, but with a displacement towards the native communities, constitutes a clear indicator of the differential admixture process that took place in different regions of Argentina. Moreover, genetic differences were observed between Patagonian localities and Bahía Blanca (Central region of Argentina). These observations warned us that population genetic constitution analysis cannot be approached without bearing in mind the regional particularities, which are the result of the different historical, migratory, social-economic and demographic processes that occurs in the country.

Este estudio tiene como objetivo el análisis de las inserciones autosómicas Alu en tres localidades de la Patagonia argentina localizadas en la región andina y costera de la provincia de Chubut. El conocimiento de la diversidad genética de estas poblaciones, junto con los datos genealógicos, contribuirán a una mejor comprensión de la información histórica, los procesos migratorios diferenciales y la composición bio-demográfica de la región central Patagónica. Para alcanzar este objetivo se analizaron 16 polimorfismos autosómicos de inserción Alu: ACE, APO-A1, TPA25, FXIIIB, A25, HS4.32, D1, HS4.69, HS2.43, Sb19.12, Yb8NBC120, Sb19.3, Yb8NBC125, Ya5NBC221, DM y CD4. Nuestros resultados mostraron que la región central Patagónica presenta una mezcla genética continental compleja de marcadas raíces nativo americanas 39% (± 1.2), eurasiáticas 56% (± 1.73) y, en menor medida, africanas 5% (± 1.7). La proximidad genética de las muestras patagónicas a los grupos de Europa y del Norte de África, pero con un mayor desplazamiento hacia las comunidades nativas, constituye un claro indicador del proceso de mezcla diferencial que tuvo lugar en las distintas regiones de la Argentina. Por otra parte, las diferencias genéticas observadas entre las localidades de Patagonia y Bahía Blanca (región central de la Argentina), nos advierten que no puede analizarse la constitución genética de las poblaciones sin tener en cuenta las particularidades regionales, que son el resultado de los diferentes procesos históricos, migratorios, socio-económicos y demográficos que ocurrieron en el interior del país.

Effects of respiratory alkalosis on human skeletal muscle metabolism at the onset of submaximal exercise.

The purpose of this study was to examine the effects of respiratory alkalosis on human skeletal muscle metabolism at rest and during submaximal exercise. Subjects exercised on two occasions for 15 min at 55 % of their maximal oxygen uptake while either hyperventilating (R-Alk) or breathing normally (Con). Muscle biopsies were taken at rest and after 1 and 15 min of exercise. At rest, no effects on muscle metabolism were observed in response to R-Alk. In the first minute of exercise, there was a delayed activation of pyruvate dehydrogenase (PDH) in R-Alk compared with Con, resulting in a reduced rate of pyruvate oxidation. Also, glycogenolysis was higher in R-Alk compared with Con, which was attributed to a higher availability of the monoprotonated form of inorganic phosphate (P(i)), resulting in an elevated rate of pyruvate production. The mismatch between pyruvate production and its oxidation resulted in net lactate accumulation. These effects were not seen after 15 min of exercise, with no further differences in muscle metabolism between conditions. The results from the present study suggest that respiratory alkalosis may play an important role in lactate accumulation during the transition from rest to exercise in acute hypoxic conditions, but that other factors mediate lactate accumulation during steady-state exercise.

Substrate utilization during exercise with glucose and glucose plus fructose ingestion in boys ages 10--14 yr.

We measured substrate utilization during exercise performed with water (W), exogenous glucose (G), and exogenous fructose plus glucose (FG) ingestion in boys age 10-14 yr. Subjects (n = 12) cycled for 90 min at 55% maximal O(2) uptake while ingesting either W (25 ml/kg), 6% G (1.5 g/kg), or 3% F plus 3% G (1.5 g/kg). Fat oxidation increased during exercise in all trials but was higher in the W (0.28 +/- 0.023 g/min) than in the G (0.24 +/- 0.023 g/min) and FG (0.25 +/- 0.029 g/min) trials (P = 0.04). Conversely, total carbohydrate (CHO) oxidation decreased in all trials and was lower in the W (0.63 +/- 0.05 g/min) than in the G (0.78 +/- 0.051 g/min) and FG (0.74 +/- 0.056 g/min) trials (P = 0.009). Exogenous CHO oxidation, as determined by expired (13)CO(2), reached a maximum of 0.36 +/- 0.032 and 0.31 +/- 0.030 g/min at 90 min in G and FG, respectively (P = 0.04). Plasma insulin levels decrease during exercise in all trials but were twofold higher in G than in W and FG (P < 0.001). Plasma glucose levels decreased transiently after the onset of exercise in all trials and then returned to preexercise values in the W and FG (approximately 4.5 mmol/l) trials but were elevated by approximately 1.0 mmol/l in the G trial (P < 0.001). Plasma lactate concentrations decreased after the onset of exercise in all trials but were lower by approximately 0.5 mmol/l in W than in G and FG (P = 0.02). Thus, in boys exercising at a moderate intensity, the oxidation rate of G plus F is slightly less than G alone, but both spare endogenous CHO and fat to a similar extent. In addition, compared with flavored W, the ingestion of G alone and of G plus F delays exhaustion at 90% peak power by approximately 25 and 40%, respectively, after 90 min of moderate-intensity exercise.

Effects of PDH activation by dichloroacetate in human skeletal muscle during exercise in hypoxia.

During the onset of exercise in hypoxia, the increased lactate accumulation is associated with a delayed activation of pyruvate dehydrogenase (PDH; Parolin ML, Spreit LL, Hultman E, Hollidge-Horvat MG, Jones NL, and Heigenhauser GJF. Am J Physiol Endocrinol Metab 278: E522-E534, 2000). The present study investigated whether activation of PDH with dichloroacetate (DCA) before exercise would reduce lactate accumulation during exercise in acute hypoxia by increasing oxidative phosphorylation. Six subjects cycled on two occasions for 15 min at 55% of their normoxic maximal oxygen uptake after a saline (control) or DCA infusion while breathing 11% O(2). Muscle biopsies of the vastus lateralis were taken at rest and after 1 and 15 min of exercise. DCA increased PDH activity at rest and at 1 min of exercise, resulting in increased acetyl-CoA concentration and acetylcarnitine concentration at rest and at 1 min. In the first minute of exercise, there was a trend toward a lower phosphocreatine (PCr) breakdown with DCA compared with control. Glycogenolysis was lower with DCA, resulting in reduced lactate concentration ([lactate]), despite similar phosphorylase a mole fractions and posttransformational regulators. During the subsequent 14 min of exercise, PDH activity was similar, whereas PCr breakdown and muscle [lactate] were reduced with DCA. Glycogenolysis was lower with DCA, despite similar mole fractions of phosphorylase a, and was due to reduced posttransformational regulators. The results from the present study support the hypothesis that lactate production is due in part to metabolic inertia and cannot solely be explained by an oxygen limitation, even under conditions of acute hypoxia.

Regulation of glycogen phosphorylase and PDH during exercise in human skeletal muscle during hypoxia.

The present study examined the acute effects of hypoxia on the regulation of skeletal muscle metabolism at rest and during 15 min of submaximal exercise. Subjects exercised on two occasions for 15 min at 55% of their normoxic maximal oxygen uptake while breathing 11% O(2) (hypoxia) or room air (normoxia). Muscle biopsies were taken at rest and after 1 and 15 min of exercise. At rest, no effects on muscle metabolism were observed in response to hypoxia. In the 1st min of exercise, glycogenolysis was significantly greater in hypoxia compared with normoxia. This small difference in glycogenolysis was associated with a tendency toward a greater concentration of substrate, free P(i), in hypoxia compared with normoxia. Pyruvate dehydrogenase activity (PDH(a)) was lower in hypoxia at 1 min compared with normoxia, resulting in a reduced rate of pyruvate oxidation and a greater lactate accumulation. During the last 14 min of exercise, glycogenolysis was greater in hypoxia despite a lower mole fraction of phosphorylase a. The greater glycogenolytic rate was maintained posttransformationally through significantly higher free [AMP] and [P(i)]. At the end of exercise, PDH(a) was greater in hypoxia compared with normoxia, contributing to a greater rate of pyruvate oxidation. Because of the higher glycogenolytic rate in hypoxia, the rate of pyruvate production continued to exceed the rate of pyruvate oxidation, resulting in significant lactate accumulation in hypoxia compared with no further lactate accumulation in normoxia. Hence, the elevated lactate production associated with hypoxia at the same absolute workload could in part be explained by the effects of hypoxia on the activities of the rate-limiting enzymes, phosphorylase and PDH, which regulate the rates of pyruvate production and pyruvate oxidation, respectively.

Effect of induced metabolic alkalosis on human skeletal muscle metabolism during exercise.

The purpose of the study was to examine the roles of active pyruvate dehydrogenase (PDH(a)), glycogen phosphorylase (Phos), and their regulators in lactate (Lac(-)) metabolism during incremental exercise after ingestion of 0.3 g/kg of either NaHCO(3) [metabolic alkalosis (ALK)] or CaCO(3) [control (CON)]. Subjects (n = 8) were studied at rest, rest postingestion, and during constant rate cycling at three stages (15 min each): 30, 60, 75% of maximal O(2) uptake (VO(2 max)). Radial artery and femoral venous blood samples, leg blood flow, and biopsies of the vastus lateralis were obtained during each power output. ALK resulted in significantly (P < 0.05) higher intramuscular Lac(-) concentration ([Lac(-)]; ALK 72.8 vs. CON 65.2 mmol/kg dry wt), arterial whole blood [Lac(-)] (ALK 8.7 vs. CON 7.0 mmol/l), and leg Lac(-) efflux (ALK 10.0 vs. CON 4.2 mmol/min) at 75% VO(2 max). The increased intramuscular [Lac(-)] resulted from increased pyruvate production due to stimulation of glycogenolysis at the level of Phos a and phosphofructokinase due to allosteric regulation mediated by increased free ADP (ADP(f)), free AMP (AMP(f)), and free P(i) concentrations. PDH(a) increased with ALK at 60% VO(2 max) but was similar to CON at 75% VO(2 max). The increased PDH(a) may have resulted from alterations in the acetyl-CoA, ADP(f), pyruvate, NADH, and H(+) concentrations leading to a lower relative activity of PDH kinase, whereas the similar values at 75% VO(2 max) may have reflected maximal activation. The results demonstrate that imposed metabolic alkalosis in skeletal muscle results in acceleration of glycogenolysis at the level of Phos relative to maximal PDH activation, resulting in a mismatch between the rates of pyruvate production and oxidation resulting in an increase in Lac(-) production.

Regulation of skeletal muscle glycogen phosphorylase and PDH during maximal intermittent exercise.

The time course for the activation of glycogen phosphorylase (Phos) and pyruvate dehydrogenase (PDH) and their allosteric regulators was determined in human skeletal muscle during repeated bouts of maximal exercise. Six subjects completed three 30-s bouts of maximal isokinetic cycling separated by 4-min recovery periods. Muscle biopsies were taken at rest and at 6, 15, and 30 s of exercise during bouts 1 and 3. Phos was rapidly activated within the first 6 s of bout 1 from 12% at rest to 47% at 6 s. The activation of PDH increased from 14% at rest to 48% at 6 s and 95% at 15 s of bout 1. Phos reverted back to basal values at the end of the first bout, whereas PDH remained fully activated. In contrast, in the third bout, PDH was 42% at rest and was activated more rapidly and was nearly completely activated by 6 s, whereas Phos remained at basal levels (range 14-20%). Lactate accumulation was marked in the first bout and increased progressively from 2.7 to 76.1 mmol/kg dry wt with no further increase in bout 3. Glycogen utilization was also marked in the first bout and was negligible in bout 3. The rapid activation of Phos and slower activation of PDH in bout 1 was probably due to Ca(2+) release from the sarcoplasmic reticulum. Lactate accumulation appeared to be due to an imbalance of the relative activities of Phos and PDH. The increase in H(+) concentration may have served to reduce pyruvate production by inhibiting Phos transformation and may have simultaneously activated PDH in the third bout such that there was a better matching between pyruvate production and oxidation and minimal lactate accumulation. As each bout progressed and with successive bouts, there was a decreasing ability to stimulate substrate phosphorylation through phosphocreatine hydrolysis and glycolysis and a shift toward greater reliance on oxidative phosphorylation.

Effect of induced metabolic acidosis on human skeletal muscle metabolism during exercise.

The roles of pyruvate dehydrogenase (PDH), glycogen phosphorylase (Phos), and their regulators in lactate (Lac(-)) metabolism were examined during incremental exercise after ingestion of 0.3 g/kg of either NH(4)Cl [metabolic acidosis (ACID)] or CaCO(3) [control (CON)]. Subjects were studied at rest, at rest postingestion, and during continuous steady-state cycling at three stages (15 min each): 30, 60, and 75% of maximal oxygen uptake. Radial artery and femoral venous blood samples, leg blood flow, and biopsies of the vastus lateralis were obtained during each power output. ACID resulted in significantly lower intramuscular concentration of [Lac(-)] (ACID 40.8 vs. CON 56.9 mmol/kg dry wt), arterial whole blood [Lac(-)] (ACID 4.7 vs. CON 6.5 mmol/l), and leg Lac(-) efflux (ACID 3.05 vs. CON 6.98 mmol. l(-1). min(-1)). The reduced intramuscular [Lac(-)] resulted from decreases in pyruvate production due to inhibition of glycogenolysis, at the level of Phos a, and phosphofructokinase, together with an increase in the amount of pyruvate oxidized relative to the total produced. The reduction in Phos a activity was mediated through decreases in transformation, decreases in free inorganic phosphate concentration, and decreases in the posttransformational allosteric regulator free AMP. Reduced PDH activity occurred with ACID and may have resulted from alterations in the concentrations of acetyl-CoA, free ADP, pyruvate, NADH, and H(+), leading to greater relative activity of the kinase. The results demonstrate that imposed metabolic acidosis in skeletal muscle results in decreased Lac(-) production due to inhibition of glycogenolysis at the level of Phos and increased pyruvate oxidation at PDH.

Role of pyruvate dehydrogenase in lactate production in exercising human skeletal muscle.

The mechanisms responsible for lactate production with increased intensity of muscle contraction are controversial. Some investigators suggest that the mitochondria are O2-limited, whereas others suggest that lactate production occurs when O2 to the mitochondria is adequate and that the increased lactate production is due to a "mass-action effect" when pyruvate production exceeds the rate of pyruvate oxidation. Pyruvate dehydrogenase is a rate-limiting enzyme for pyruvate entry into the tricarboxylic acid cycle; its catalytic activity influences both pyruvate oxidation and lactate production. Since lactate dehydrogenase is an equilibrium enzyme, increased lactate production will be due to a mass-action effect exerted by increases in pyruvate concentrations. Because the equilibrium constant of the lactate dehydrogenase reaction markedly favors lactate over pyruvate, small increases in pyruvate concentration will result in large increases in lactate concentration. At higher exercise intensities, which are more reliant on glycogen as substrate, the rate of pyruvate production exceeds the catalytic activity of pyruvate dehydrogenase, and lactate production occurs. Studies using dichloroacetate, induced acid-base changes, diet and short-term endurance training, indicate that lactate production is related to complex interactions of metabolic pathways and not related to inadequate O2 supply. As pyruvate dehydrogenase plays a central role in the integration of carbohydrate and fat metabolism, and in the entry of pyruvate into the tricarboxylic acid cycle, this enzyme plays a key role in lactate production.

Regulation of skeletal muscle glycogen phosphorylase and PDH at varying exercise power outputs.

This study investigated the transformational and posttransformational control of skeletal muscle glycogen phosphorylase and pyruvate dehydrogenase (PDH) at three exercise power outputs [35, 65, and 90% of maximal oxygen uptake (VO2 max)]. Seven untrained subjects cycled at one power output for 10 min on three separate occasions, with muscle biopsies at rest and 1 and 10 min of exercise. Glycogen phosphorylase in the more active (a) form was not significantly different at any time across power outputs (21. 4-29.6%), with the exception of 90%, where it fell significantly to 15.3% at 10 min. PDH transformation increased significantly from rest (average 0.53 mmol . kg wet muscle-1 . min-1) to 1 min of exercise as a function of power output (1.60 +/- 0.26, 2.77 +/- 0.29, and 3.33 +/- 0.31 mmol . kg wet muscle-1 . min-1 at 35, 65, and 90%, respectively) with a further significant increase at 10 min (4.45 +/- 0.35) at 90% VO2 max. Muscle lactate, acetyl-CoA, acetylcarnitine, and free ADP, AMP, and Pi were unchanged from rest at 35% VO2 max but rose significantly at 65 and 90%, with accumulations at 90% being significantly higher than 65%. The results of this study indicate that glycogen phosphorylase transformation is independent of increasing power outputs, despite increasing glycogenolytic flux, suggesting that flux through glycogen phosphorylase is matched to the demand for energy by posttransformational factors, such as free Pi and AMP. Conversely, PDH transformation is directly related to the increasing power output and the calculated flux through the enzyme. The rise in PDH transformation is likely due to increased Ca2+ concentration and/or increased pyruvate. These results demonstrate that metabolic signals related to contraction and the energy state of the cell are sensitive to the exercise intensity and coordinate the increase in carbohydrate use with increasing power output.