Oral Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes

BackgroundEstablishing cardiovascular safety of new therapies for type 2 diabetes is important. Safety data are available for the subcutaneous form of the glucagon-like peptide-1 receptor agonist semaglutide but are needed for oral semaglutide.MethodsWe assessed cardiovascular outcomes of once-daily oral semaglutide in an event-driven, randomized, double-blind, placebo-controlled trial involving patients at high cardiovascular risk (age of >= 50 years with established cardiovascular or chronic kidney disease, or age of >= 60 years with cardiovascular risk factors only). The primary outcome in a time-to-event analysis was the first occurrence of a major adverse cardiovascular event (death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke). The trial was designed to rule out 80% excess cardiovascular risk as compared with placebo (noninferiority margin of 1.8 for the upper boundary of the 95% confidence interval for the hazard ratio for the primary outcome).ResultsA total of 3183 patients were randomly assigned to receive oral semaglutide or placebo. The mean age of the patients was 66 years; 2695 patients (84.7%) were 50 years of age or older and had cardiovascular or chronic kidney disease. The median time in the trial was 15.9 months. Major adverse cardiovascular events occurred in 61 of 1591 patients (3.8%) in the oral semaglutide group and 76 of 1592 (4.8%) in the placebo group (hazard ratio, 0.79; 95% confidence interval [CI], 0.57 to 1.11; P<0.001 for noninferiority). Results for components of the primary outcome were as follows: death from cardiovascular causes, 15 of 1591 patients (0.9%) in the oral semaglutide group and 30 of 1592 (1.9%) in the placebo group (hazard ratio, 0.49; 95% CI, 0.27 to 0.92); nonfatal myocardial infarction, 37 of 1591 patients (2.3%) and 31 of 1592 (1.9%), respectively (hazard ratio, 1.18; 95% CI, 0.73 to 1.90); and nonfatal stroke, 12 of 1591 patients (0.8%) and 16 of 1592 (1.0%), respectively (hazard ratio, 0.74; 95% CI, 0.35 to 1.57). Death from any cause occurred in 23 of 1591 patients (1.4%) in the oral semaglutide group and 45 of 1592 (2.8%) in the placebo group (hazard ratio, 0.51; 95% CI, 0.31 to 0.84). Gastrointestinal adverse events leading to discontinuation of oral semaglutide or placebo were more common with oral semaglutide.ConclusionsIn this trial involving patients with type 2 diabetes, the cardiovascular risk profile of oral semaglutide was not inferior to that of placebo

mTORC1 Inhibition via Rapamycin Promotes Triacylglycerol Lipolysis and Release of Free Fatty Acids in 3T3â L1 Adipocytes

Signaling by mTOR complex 1 (mTORC1) promotes anabolic cellular processes in response to growth factors, nutrients, and hormonal cues. Numerous clinical trials employing the mTORC1 inhibitor rapamycin (aka sirolimus) to immunoâ suppress patients following organ transplantation have documented the development of hypertriglyceridemia and elevated serum free fatty acids (FFA). We therefore investigated the cellular role of mTORC1 in control of triacylglycerol (TAG) metabolism using cultured murine 3T3â L1 adipocytes. We found that treatment of adipocytes with rapamycin reduced insulinâ stimulated TAG storage ~50%. To determine whether rapamycin reduces TAG storage by upregulating lipolytic rate, we treated adipocytes in the absence and presence of rapamycin and isoproterenol, a β2â adrenergic agonist that activates the cAMP/protein kinase A (PKA) pathway to promote lipolysis. We found that rapamycin augmented isoproterenolâ induced lipolysis without altering cAMP levels. Rapamycin enhanced the isoproterenolâ stimulated phosphorylation of hormone sensitive lipase (HSL) on Serâ 563 (a PKA site), but had no effect on the phosphorylation of HSL S565 (an AMPK site). Additionally, rapamycin did not affect the isoproterenolâ mediated phosphorylation of perilipin, a protein that coats the lipid droplet to initiate lipolysis upon phosphorylation by PKA. These data demonstrate that inhibition of mTORC1 signaling synergizes with the βâ adrenergicâ cAMP/PKA pathway to augment phosphorylation of HSL to promote hormoneâ induced lipolysis. Moreover, they reveal a novel metabolic function for mTORC1; mTORC1 signaling suppresses lipolysis, thus augmenting TAG storage.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141428/1/lipd1089.pd

Contractions induce phosphorylation of the AMPK site Ser(565) in hormone-sensitive lipase in muscle

Intramyocellular triglyceride is an important energy store which is related to insulin resistance. Mobilization of fatty acids from this pool is probably regulated by hormone-sensitive lipase (HSL), which has recently been shown to exist in muscle and to be activated by epinephrine via PKA and by contractions via PKC and ERK. 5' AMP-activated protein kinase (AMPK) is an intracellular fuel gauge which regulates metabolism. In this Study we incubated rat soleus Muscle to investigate if AMPK influences HSL during 5 min of repeated tetanic contractions. An eightfold increase in AMPK activity was accompanied by a 2.5-fold increase in phosphorylation of the AMPK-site Ser(565) in HSL (p < 0.05). Inhibition of PKC by Calphostin C abolished the contraction-mediated HSL activation while HSL-Ser(565) phosphorylation was not reduced. The study indicates that during contractions AMPK phosphorylates HSL in Ser(565), but this phosphorylation is not directly responsible for the contraction-induced activation of HSL

Regulation and role of hormone-sensitive lipase in rat skeletal muscle

Intramyocellular triacylglycerol (TG) is an important energy store, and the energy content of this depot is higher than the energy content of the muscle glycogen depot. It has recently been shown that the mobilization of fatty acids from this TG pool may be regulated by the neutral lipase hormone-sensitive lipase (HSL). This enzyme is known to be rate limiting for intracellular TG hydrolysis in adipose tissue. The presence of HSL has been demonstrated in all muscle fibre types by Western blotting of muscle fibres isolated by collagenase treatment or after freeze-drying. The content of HSL varies between fibre types, being higher in oxidative fibres than in glycolytic fibres. When analysed under conditions optimal for HSL, neutral lipase activity in muscle can be stimulated by adrenaline as well as by contractions. These increases are abolished by the presence of anti-HSL antibody during analysis. Moreover, immunoprecipitation with affinity-purified anti-HSL antibody causes similar reductions in muscle HSL protein concentration and in measured neutral lipase responses to contractions. The immunoreactive HSL in muscle is stimulated by adrenaline via beta-adrenergic activation of cAMP-dependent protein kinase (PKA). From findings in adipocytes it is likely that PKA phosphorylates HSL at residues Ser(563), Ser(659) and Ser(660). Contraction probably also enhances muscle HSL activity by phosphorylation, because the contraction-induced increase in HSL activity is elevated by the protein phosphatase inhibitor okadaic acid and reversed by alkaline phosphatase. A novel signalling pathway in muscle by which HSL activity may be stimulated by protein kinase C (PKC) via extracellular signal-regulated kinase (ERK) has been demonstrated. In contrast to previous findings in adipocytes, in muscle the activation of ERK is not necessary for stimulation of HSL by adrenaline. However, contraction-induced HSL activation is mediated by PKC, at least partly via the ERK pathway. In fat cells ERK is known to phosphorylate HSL at Ser(600). Hence, phosphorylation of different sites may explain the finding that in muscle the effects of contractions and adrenaline on HSL activity are partially additive. In line with the view that the two stimuli act by different mechanisms, training increases contraction-mediated HSL activation but diminishes adrenaline-mediated HSL activation in muscle. In conclusion, HSL is present in skeletal muscle and can be activated by phosphorylation in response to both adrenaline and muscle contractions. Training increases contraction-mediated HSL activation, but decreases adrenaline-mediated HSL activation in muscle

Hormone-sensitive lipase in skeletal muscle: regulatory mechanisms.

AIM: The enzymatic regulation of intramuscular triacylglycerol (TG) breakdown has until recently not been well understood. Our aim was to elucidate the role of hormone-sensitive lipase (HSL), which controls TG breakdown in adipose tissue. METHODS: Isolated rat muscle as well as exercising humans were studied. RESULTS: The presence of HSL was demonstrated in all muscle fibre types by Western blotting of muscle fibres isolated by collagenase treatment or after freeze-drying. The content of HSL varies between fibre types, being higher in oxidative than in glycolytic fibres. Analysed under conditions optimal for HSL, neutral lipase activity in muscle can be stimulated by adrenaline as well as by contractions. These increases are abolished by presence of anti-HSL antibody during analysis. Moreover, immunoprecipitation with affinity-purified anti-HSL antibody causes similar reductions in muscle HSL protein concentration and in measured neutral lipase responses to contractions. The immunoreactive HSL in muscle is stimulated by adrenaline via beta-adrenergic activation of protein kinase A (PKA). From findings in adipocytes it is likely that PKA phosphorylates HSL at residues Ser563, Ser659 and Ser660. Contraction probably also enhances muscle-HSL activity by phosphorylation, because the contraction-induced increase in HSL activity is increased by the protein phosphatase inhibitor okadaic acid and reversed by alkaline phosphatase. A novel signalling pathway in muscle by which HSL activity may be stimulated by protein kinase C (PKC) via extracellular signal regulated kinase (ERK) has been demonstrated. In contrast to previous findings in adipocytes, in muscle activation of ERK is not necessary for stimulation of HSL by adrenaline. However, contraction-induced HSL activation is mediated by PKC, at least partly via the ERK pathway. In fat cells ERK is known to phosphorylate HSL at Ser600. So, phosphorylation of different sites may explain that in muscle the effects of contractions and adrenaline on HSL activity are partially additive. In line with the view that the two stimuli act by different mechanisms, training increases the contraction-mediated, but diminishes the adrenaline mediated HSL activation in muscle. CONCLUSION: The existence and regulation of HSL in skeletal muscle indicate a role of HSL in muscle TG metabolism