AMPK activation by SC4 inhibits noradrenaline-induced lipolysis and insulin-stimulated lipogenesis in white adipose tissue.

The effects of small-molecule AMP-activated protein kinase (AMPK) activators in rat epididymal adipocytes were compared. SC4 was the most effective and submaximal doses of SC4 and 5-amino-4-imidazolecarboxamide (AICA) riboside were combined to study the effects of AMPK activation in white adipose tissue (WAT). Incubation of rat adipocytes with SC4 + AICA riboside inhibited noradrenaline-induced lipolysis and decreased hormone-sensitive lipase (HSL) Ser563 phosphorylation, without affecting HSL Ser565 phosphorylation. Preincubation of fat pads from wild-type (WT) mice with SC4 + AICA riboside inhibited insulin-stimulated lipogenesis from glucose or acetate and these effects were lost in AMPKα1 knockout (KO) mice, indicating AMPKα1 dependency. Moreover, in fat pads from acetyl-CoA carboxylase (ACC)1/2 S79A/S212A double knockin versus WT mice, the effect of SC4 + AICA riboside to inhibit insulin-stimulated lipogenesis from acetate was lost, pinpointing ACC as the main AMPK target. Treatment with SC4 + AICA riboside decreased insulin-stimulated glucose uptake, an effect that was still observed in fat pads from AMPKα1 KO versus WT mice, suggesting the effect was partly AMPKα1-independent. SC4 + AICA riboside treatment had no effect on the insulin-induced increase in palmitate esterification nor on sn-glycerol-3-phosphate-O-acyltransferase activity. Therefore in WAT, AMPK activation inhibits noradrenaline-induced lipolysis and suppresses insulin-stimulated lipogenesis primarily by inactivating ACC and by inhibiting glucose uptake.

Whole-life body composition trajectory and longevity: role of insulin.

The present study assessed the body composition trajectory of rats (N = 96) placed into 5 groups according to lifespan, using dual-energy x-ray absorptiometry every 6 months until end-of-life. A striking linearity between lifespan and bone mass percentage (not absolute bone mass) was observed. Long-lived rats show a higher bone mass percentage with a delayed insulin rise to a similar peak level as short-lived counterparts, followed by insulin declines and bone mass loss. Decreasing insulin after streptozotocin (STZ) injection caused a rapid bone mass loss (-10.5%) with a decreased 5-day survival rate to 35% in old rats (20 months). Insulin replacement to STZ-injected rats completely blocked bone mass loss and increased the survival rate to 71%. Normal old rats (20 months) had faster lean mass loss despite greater myofiber regeneration (centronucleation) compared with the young rats (4 months). Increased CD68+ and CD163+ cell infiltration into insulin-depleted muscle suggests a bone marrow cell exhaustion by aging muscle. Bone produces stem cells and phagocytes to continuously rejuvenate peripheral tissues. Our data suggests that aging and unsustainable life is associated with development of disproportionality between bone and the growing body size, partly due to insulin reversal from hyperinsulinemia during late life.

Effects of PKB/Akt inhibitors on insulin-stimulated lipogenesis and phosphorylation state of lipogenic enzymes in white adipose tissue.

We investigated acute effects of two allosteric protein kinase B (PKB) inhibitors, MK-2206 and Akti-1/2, on insulin-stimulated lipogenesis in rat epididymal adipocytes incubated with fructose as carbohydrate substrate. In parallel, the phosphorylation state of lipogenic enzymes in adipocytes and incubated epididymal fat pads was monitored by immunoblotting. Preincubation of rat epididymal adipocytes with PKB inhibitors dose-dependently inhibited the following: insulin-stimulated lipogenesis, increased PKB Ser473 phosphorylation, increased PKB activity and decreased acetyl-CoA carboxylase (ACC) Ser79 phosphorylation. In contrast, the effect of insulin to decrease the phosphorylation of pyruvate dehydrogenase (PDH) at Ser293 and Ser300 was not abolished by PKB inhibition. Insulin treatment also induced ATP-citrate lyase (ACL) Ser454 phosphorylation, but this effect was less sensitive to PKB inhibitors than ACC dephosphorylation by insulin. In incubated rat epididymal fat pads, Akti-1/2 treatment reversed insulin-induced ACC dephosphorylation, while ACL phosphorylation by insulin was maintained. ACL and ACC purified from white adipose tissue were poor substrates for PKBα in vitro. However, effects of wortmannin and torin, along with Akti-1/2 and MK-2206, on recognized PKB target phosphorylation by insulin were similar to their effects on insulin-induced ACL phosphorylation, suggesting that PKB could be the physiological kinase for ACL phosphorylation by insulin. In incubated epididymal fat pads from wild-type versus ACC1/2 S79A/S212A knockin mice, effects of insulin to increase lipogenesis from radioactive fructose or from radioactive acetate were reduced but not abolished. Together, the results support a key role for PKB in mediating insulin-stimulated lipogenesis by decreasing ACC phosphorylation, but not by decreasing PDH phosphorylation.

Can Match-Mimicking Intermittent Practice Be Used as a Simulatory Training Mode of Competition Using Olympic Time Frame in Elite Taekwondo Athletes?

Aim: The physiological realities between Taekwondo (TKD) simulation kicking training and TKD competition according to the Olympic time frame remain unclear. The purpose of this study is to establish an Olympic match-simulated kicking model and compare its effects with real TKD competition on physiological challenges and hormonal responses during serial matches in elite athletes. Method: Sixteen elite TKD athletes randomly were assigned into either a TKD match-simulated kicking group (TMSK; N = 8, age: 21.3 ± 0.2 years) or a simulated TKD competition group (STC; N = 8, age: 21.6 ± 0.5 years). Both groups performed either simulated kicking or TKD competitions in the same time-course order, and all physiological parameters and blood sampling time-points were identical between groups. The heart rate (HR) and rating of perceived exertion (RPE) were recorded during each match-simulated kicking and TKD competition session. Blood samples were obtained before competition (Pre-Comp.), after competition-in ths case meaning four consecutive matches (End-Comp.), and 24 h after the first match (Next day) for determination of biomarkers of muscle damage (myoglobin and CK), hematological profiles, and hormonal profiles (testosterone and cortisol). Results: The responses of HR, RPE, and blood lactate levels during the consecutive testing sessions showed no differences between TMSK and STC. The changes in CK and myoglobin were greater in STC (p < 0.05), and a greater decrease in red blood cell (RBC) loss was observed in the STC group (p < 0.05). Compared with TMSK, the inflammatory state, reflected by the ratios of neutrophils-to-lymphocyte (NLR) and platelets-to-lymphocyte (PLR), was higher in STC (p < 0.05). Moreover, the catabolic state (cortisol/testosterone) was greater in STC than in TMSK (p < 0.05). Conclusion: We demonstrated that, compared with TMSK, the STC produced greater muscle damage, inflammatory responses, and catabolic stress in the Olympic competition time frame in elite male TKD athletes. Although TMSK is capable of eliciting similar physiological challenges as TKD competition, the muscle damage and hormonal profiles provoked by TMSK were not comparable to TKD competition. Our findings provide science-based data and better understanding for coaches, athletes, and sports scientists to develop TKD-specific training programs for Olympic preparation.

Genetic deletion of soluble 5'-nucleotidase II reduces body weight gain and insulin resistance induced by a high-fat diet.

We previously investigated whether inhibition of AMP-metabolizing enzymes could enhance AMP-activated protein kinase (AMPK) activation in skeletal muscle for the treatment of type 2 diabetes. Soluble 5'-nucleotidase II (NT5C2) hydrolyzes IMP and its inhibition could potentially lead to a rise in AMP to activate AMPK. In the present study, we investigated effects of NT5C2 deletion in mice fed a normal-chow diet (NCD) or a high-fat diet (HFD). On a NCD, NT5C2 deletion did not result in any striking metabolic phenotype. On a HFD however, NT5C2 knockout (NT5C2-/-) mice displayed reduced body/fat weight gain, improved glucose tolerance, reduced plasma insulin, triglyceride and uric acid levels compared with wild-type (WT) mice. There was a tendency towards smaller and fewer adipocytes in epididymal fat from NT5C2-/- mice compared to WT mice, consistent with a reduction in triglyceride content. Differences in fat mass under HFD could not be explained by changes in mRNA expression profiles of epididymal fat from WT versus NT5C2-/- mice. However, rates of lipolysis tended to increase in epididymal fat pads from NT5C2-/- versus WT mice, which might explain reduced fat mass. In incubated skeletal muscles, insulin-stimulated glucose uptake and associated signalling were enhanced in NT5C2-/- versus WT mice on HFD, which might contribute towards improved glycemic control. In summary, NT5C2 deletion in mice protects against HFD-induced weight gain, adiposity, insulin resistance and associated hyperglycemia.

Can mesenchymal stem cell lysate reverse aging?

Recent findings regarding uses of adipose-derived mesenchymal stem cell (MSC)-lysate on weight loss and improved glucose tolerance in mice on a high-fat diet suggest an encouraging possibility of using MSC lysate for an anti-aging intervention in humans. However, weight loss and lipopenia during late life can be as life-threatening as hyperglycemia during early adulthood. For this 3-year lifelong experiment, a total of 92 rats were randomized into the vehicle-injected group (F=22; M=24) and the MSC lysate injected group (F=22, M=24). We examined longevity, spontaneous locomotor activity, and body composition in rats maintained on a normal diet and received an intermittent treatment of human adipose-derived MSC lysate (3 times a week, 11 times a month given every second month), starting at 12 months of age until natural death. In substantiating previous knowledge regarding the effects of long-term MSC lysate treatments on fat loss and insulin resistance, the present findings also highlighted a shortened average lifespan, a longer inactive time, and a greater bone loss with a relative increase of lean mass in MSC lysate rats with respect to controls. Conclusion: Our data suggest that MSC lysate treatments stimulate disparity in tissue development and produce a cachexia-like effect to decrease longevity.

Improved inflammatory balance of human skeletal muscle during exercise after supplementations of the ginseng-based steroid Rg1.

UNLABELLED: The purpose of the study was to determine the effect of ginseng-based steroid Rg1 on TNF-alpha and IL-10 gene expression in human skeletal muscle against exercise challenge, as well as on its ergogenic outcomes. Randomized double-blind placebo-controlled crossover trials were performed, separated by a 4-week washout. Healthy young men were randomized into two groups and received capsule containing either 5 mg of Rg1 or Placebo one night and one hour before exercise. Muscle biopsies were conducted at baseline, immediately and 3 h after a standardized 60-min cycle ergometer exercise. While treatment differences in glycogen depletion rate of biopsied quadriceps muscle during exercise did not reach statistical significance, Rg1 supplementations enhanced post-exercise glycogen replenishment and increased citrate synthase activity in the skeletal muscle 3 h after exercise, concurrent with improved meal tolerance during recovery (P<0.05). Rg1 suppressed the exercise-induced increases in thiobarbituric acids reactive substance (TBARS) and reversed the increased TNF-alpha and decreased IL-10 mRNA of quadriceps muscle against the exercise challenge. PGC-1 alpha and GLUT4 mRNAs of exercised muscle were not affected by Rg1. Maximal aerobic capacity (VO2max) was not changed by Rg1. However, cycling time to exhaustion at 80% VO2max increased significantly by ~20% (P<0.05). CONCLUSION: Our result suggests that Rg1 is an ergogenic component of ginseng, which can minimize unwanted lipid peroxidation of exercised human skeletal muscle, and attenuate pro-inflammatory shift under exercise challenge.