Mitochondria regulate critical components of cellular function via ATP production, reactive oxygen species production, Ca(2+) handling and apoptotic signaling. Two classical methods exist to study ...mitochondrial function of skeletal muscles: isolated mitochondria and permeabilized myofibers. Whereas mitochondrial isolation removes a portion of the mitochondria from their cellular environment, myofiber permeabilization preserves mitochondrial morphology and functional interactions with other intracellular components. Despite this, isolated mitochondria remain the most commonly used method to infer in vivo mitochondrial function. In this study, we directly compared measures of several key aspects of mitochondrial function in both isolated mitochondria and permeabilized myofibers of rat gastrocnemius muscle. Here we show that mitochondrial isolation i) induced fragmented organelle morphology; ii) dramatically sensitized the permeability transition pore sensitivity to a Ca(2+) challenge; iii) differentially altered mitochondrial respiration depending upon the respiratory conditions; and iv) dramatically increased H(2)O(2) production. These alterations are qualitatively similar to the changes in mitochondrial structure and function observed in vivo after cellular stress-induced mitochondrial fragmentation, but are generally of much greater magnitude. Furthermore, mitochondrial isolation markedly altered electron transport chain protein stoichiometry. Collectively, our results demonstrate that isolated mitochondria possess functional characteristics that differ fundamentally from those of intact mitochondria in permeabilized myofibers. Our work and that of others underscores the importance of studying mitochondrial function in tissue preparations where mitochondrial structure is preserved and all mitochondria are represented.
Males of many species choose their mate according to the female's reproductive status, and there is now increasing evidence that male fitness can depend on this discrimination. However, females will ...also aim to regulate their mating activity so as to maximize their own fitness. As such, both sexes may attempt to dictate the frequency and timing of female mating, reflecting the potentially different costs of female signaling to both sexes. Here, I review evidence that chemical cues and signals are used widely by males to discriminate between mated and unmated females, and explore the mechanisms by which female odour changes post‐mating. There is substantial empirical evidence that mated and unmated females differ in their chemical profile, and that this variation provides males with information on a female's mating status. Although there appears to be large variation among species regarding the mechanisms by which female odour is altered post‐mating, the transfer of male substances to females during or subsequent to copulation appear to play a major role. This transfer of substances by males may be part of their strategy to suppress reproduction by competing males, particularly in species where females mate more than once.
Abstract
Context
Novel dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist (RA) tirzepatide demonstrated substantially greater glucose control ...and weight loss (WL) compared with selective GLP-1RA dulaglutide.
Objective
Explore mechanisms of glucose control by tirzepatide.
Design
Post hoc analyses of fasting biomarkers and multiple linear regression analysis.
Setting
Forty-seven sites in 4 countries.
Patients or other Participants
Three hundred and sixteen subjects with type 2 diabetes.
Interventions
Tirzepatide (1, 5, 10, 15 mg), dulaglutide (1.5 mg), placebo.
Main Outcome Measures
Analyze biomarkers of beta-cell function and insulin resistance (IR) and evaluate WL contributions to IR improvements at 26 weeks.
Results
Homeostatic model assessment (HOMA) 2-B significantly increased with dulaglutide and tirzepatide 5, 10, and 15 mg compared with placebo (P ≤ .02). Proinsulin/insulin and proinsulin/C-peptide ratios significantly decreased with tirzepatide 10 and 15 mg compared with placebo and dulaglutide (P ≤ .007). Tirzepatide 10 and 15 mg significantly decreased fasting insulin (P ≤ .033) and tirzepatide 10 mg significantly decreased HOMA2-IR (P = .004) compared with placebo and dulaglutide. Markers of improved insulin sensitivity (IS) adiponectin, IGFBP-1, and IGFBP-2 significantly increased by 1 or more doses of tirzepatide (P < .05). To determine whether improvements in IR were directly attributable to WL, multiple linear regression analysis with potential confounding variables age, sex, metformin, triglycerides, and glycated hemoglobin A1c was conducted. WL significantly (P ≤ .028) explained only 13% and 21% of improvement in HOMA2-IR with tirzepatide 10 and 15 mg, respectively.
Conclusions
Tirzepatide improved markers of IS and beta-cell function to a greater extent than dulaglutide. IS effects of tirzepatide were only partly attributable to WL, suggesting dual receptor agonism confers distinct mechanisms of glycemic control.
A thoughtfully constructed syllabus can be transformative for your students' learning, communicating the path they can take to succeed. This book demonstrates how, rather than being a mundane ...document to convey policies, you can construct your syllabus to be a motivating resource that conveys a clear sense of your course's learning goals, how students can achieve those goals, and makes evident your teaching philosophy and why you have adopted the teaching strategies you will use, such as discussion or group activities. Developing or revising a syllabus also presents you with a perfect opportunity to review the learning possibilities for the semester. Well-designed, it can help you stay focused on achieving the learning outcomes, as well as determine if the class is on track and whether adjustments to the schedule are needed. The authors show how, by adopting a welcoming tone and clearly stating learning outcomes, your syllabus can engage students by explaining the relevance of your course to their studies, create an all-important positive first impression of you as an instructor, and guide students through the resources you will be using, the assignments ahead, as well as clear guidance on how they will be assessed. Referred to frequently as the course progresses, an effective syllabus will keep students engaged and on task.Christine Harrington and Melissa Thomas lead you through all the elements of a syllabus to help you identify how to present key messages and information about your course, think through the impressions you want to create, and, equally importantly, suggest how you can use layout and elements such as images and charts to make your syllabus visually appealing and easy to navigate.
Fibroblast growth factor 21 (FGF21), a hormone implicated in the regulation of glucose homoeostasis, insulin sensitivity, lipid metabolism and body weight, is considered to be a promising therapeutic ...target for the treatment of metabolic disorders. Despite observations that FGF21 is rapidly proteolysed in circulation rending it potentially inactive, little is known regarding mechanisms by which FGF21 protein levels are regulated. We systematically investigated human FGF21 protein processing using mass spectrometry. In agreement with previous reports, circulating human FGF21 was found to be cleaved primarily after three proline residues at positions 2, 4 and 171. The extent of FGF21 processing was quantified in a small cohort of healthy human volunteers. Relative abundance of FGF21 proteins cleaved after Pro-2, Pro-4 and Pro-171 ranged from 16 to 30%, 10 to 25% and 10 to 34%, respectively. Dipeptidyl peptidase IV (DPP-IV) was found to be the primary protease responsible for N-terminal cleavages after residues Pro-2 and Pro-4. Importantly, fibroblast activation protein (FAP) was implicated as the protease responsible for C-terminal cleavage after Pro-171, rendering the protein inactive. The requirement of FAP for FGF21 proteolysis at the C-terminus was independently demonstrated by in vitro digestion, immunodepletion of FAP in human plasma, administration of an FAP-specific inhibitor and by human FGF21 protein processing patterns in FAP knockout mouse plasma. The discovery that FAP is responsible for FGF21 inactivation extends the FGF21 signalling pathway and may enable novel approaches to augment FGF21 actions for therapeutic applications.
According to current consensus guidelines for type 2 diabetes management, bodyweight management is as important as attaining glycaemic targets. Retatrutide, a single peptide with agonist activity at ...the glucose-dependent insulinotropic polypeptide (GIP), GLP-1, and glucagon receptors, showed clinically meaningful glucose-lowering and bodyweight-lowering efficacy in a phase 1 study. We aimed to examine the efficacy and safety of retatrutide in people with type 2 diabetes across a range of doses.
In this randomised, double-blind, double-dummy, placebo-controlled and active comparator-controlled, parallel-group, phase 2 trial, participants were recruited from 42 research and health-care centres in the USA. Adults aged 18–75 years with type 2 diabetes, glycated haemoglobin (HbA1c) of 7·0–10·5% (53·0–91·3 mmol/mol), and BMI of 25–50 kg/m2 were eligible for enrolment. Eligible participants were treated with diet and exercise alone or with a stable dose of metformin (≥1000 mg once daily) for at least 3 months before the screening visit. Participants were randomly assigned (2:2:2:1:1:1:1:2) using an interactive web-response system, with stratification for baseline HbA1c and BMI, to receive once-weekly injections of placebo, 1·5 mg dulaglutide, or retatrutide maintenance doses of 0·5 mg, 4 mg (starting dose 2 mg), 4 mg (no escalation), 8 mg (starting dose 2 mg), 8 mg (starting dose 4 mg), or 12 mg (starting dose 2 mg). Participants, study site personnel, and investigators were masked to treatment allocation until after study end. The primary endpoint was change in HbA1c from baseline to 24 weeks, and secondary endpoints included change in HbA1c and bodyweight at 36 weeks. Efficacy was analysed in all randomly assigned, except inadvertently enrolled, participants, and safety was assessed in all participants who received at least one dose of study treatment. The study is registered at ClinicalTrials.gov, NCT04867785.
Between May 13, 2021, and June 13, 2022, 281 participants (mean age 56·2 years SD 9·7, mean duration of diabetes 8·1 years 7·0, 156 56% female, and 235 84% White) were randomly assigned and included in the safety analysis (45 in the placebo group, 46 in the 1·5 mg dulaglutide group, and 47 in the retatrutide 0·5 mg group, 23 in the 4 mg escalation group, 24 in the 4 mg group, 26 in the 8 mg slow escalation group, 24 in the 8 mg fast escalation group, and 46 in the 12 mg escalation group). 275 participants were included in the efficacy analyses (one each in the retatrutide 0·5 mg group, 4 mg escalation group, and 8 mg slow escalation group, and three in the 12 mg escalation group were inadvertently enrolled). 237 (84%) participants completed the study and 222 (79%) completed study treatment. At 24 weeks, least-squares mean changes from baseline in HbA1c with retatrutide were –0·43% (SE 0·20; –4·68 mmol/mol 2·15) for the 0·5 mg group, –1·39% (0·14; –15·24 mmol/mol 1·56) for the 4 mg escalation group, –1·30% (0·22; –14·20 mmol/mol 2·44) for the 4 mg group, –1·99% (0·15; –21·78 mmol/mol 1·60) for the 8 mg slow escalation group, –1·88% (0·21; –20·52 mmol/mol 2·34) for the 8 mg fast escalation group, and –2·02% (0·11; –22·07 mmol/mol 1·21) for the 12 mg escalation group, versus –0·01% (0·21; –0·12 mmol/mol 2·27) for the placebo group and –1·41% (0·12; –15·40 mmol/mol 1·29) for the 1·5 mg dulaglutide group. HbA1c reductions with retatrutide were significantly greater (p<0·0001) than placebo in all but the 0·5 mg group and greater than 1·5 mg dulaglutide in the 8 mg slow escalation group (p=0·0019) and 12 mg escalation group (p=0·0002). Findings were consistent at 36 weeks. Bodyweight decreased dose dependently with retatrutide at 36 weeks by 3·19% (SE 0·61) for the 0·5 mg group, 7·92% (1·28) for the 4 mg escalation group, 10·37% (1·56) for the 4 mg group, 16·81% (1·59) for the 8 mg slow escalation group, 16·34% (1·65) for the 8 mg fast escalation group, and 16·94% (1·30) for the 12 mg escalation group, versus 3·00% (0·86) with placebo and 2·02% (0·72) with 1·5 mg dulaglutide. For retatrutide doses of 4 mg and greater, decreases in weight were significantly greater than with placebo (p=0·0017 for the 4 mg escalation group and p<0·0001 for others) and 1·5 mg dulaglutide (all p<0·0001). Mild-to-moderate gastrointestinal adverse events, including nausea, diarrhoea, vomiting, and constipation, were reported in 67 (35%) of 190 participants in the retatrutide groups (from six 13% of 47 in the 0·5 mg group to 12 50% of 24 in the 8 mg fast escalation group), six (13%) of 45 participants in the placebo group, and 16 (35%) of 46 participants in the 1·5 mg dulaglutide group. There were no reports of severe hypoglycaemia and no deaths during the study.
In people with type 2 diabetes, retatrutide showed clinically meaningful improvements in glycaemic control and robust reductions in bodyweight, with a safety profile consistent with GLP-1 receptor agonists and GIP and GLP-1 receptor agonists. These phase 2 data also informed dose selection for the phase 3 programme.
Eli Lilly and Company.
With an increasing prevalence of obesity, there is a need for new therapies to improve body weight management and metabolic health. Multireceptor agonists in development may provide approaches to ...fulfill this unmet medical need. LY3437943 is a novel triple agonist peptide at the glucagon receptor (GCGR), glucose-dependent insulinotropic polypeptide receptor (GIPR), and glucagon-like peptide-1 receptor (GLP-1R). In vitro, LY3437943 shows balanced GCGR and GLP-1R activity but more GIPR activity. In obese mice, administration of LY3437943 decreased body weight and improved glycemic control. Body weight loss was augmented by the addition of GCGR-mediated increases in energy expenditure to GIPR- and GLP-1R-driven calorie intake reduction. In a phase 1 single ascending dose study, LY3437943 showed a safety and tolerability profile similar to other incretins. Its pharmacokinetic profile supported once-weekly dosing, and a reduction in body weight persisted up to day 43 after a single dose. These findings warrant further clinical assessment of LY3437943.
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•LY3437943 has triple agonist activity at the glucagon, GIP, and GLP-1 receptors•LY3437943 caused greater body weight loss in obese mice than tirzepatide•LY3437943 increased energy expenditure through glucagon receptor activation•Safety and tolerability of LY3437943 were similar to other incretin-based drugs
Coskun et al. demonstrate that LY3437943, a triple glucagon, GIP, and GLP-1 receptor agonist for the treatment of obesity and type 2 diabetes, can reduce body weight through increased energy expenditure and reduced calorie intake in obese mice. Its safety and tolerability in healthy participants were similar to other incretin-based therapies.
Polypharmacy is common in patients with nonalcoholic fatty liver disease (NAFLD) and previous reports suggest that NAFLD is associated with altered drug disposition. This study aims to determine if ...patients with NAFLD are at risk for altered drug response by characterizing changes in hepatic mRNA expression of genes mediating drug disposition (pharmacogenes) across the histological NAFLD severity spectrum. We utilize RNA-seq for 93 liver biopsies with histologically staged NAFLD Activity Score (NAS), fibrosis stage, and steatohepatitis (NASH). We identify 37 significant pharmacogene-NAFLD severity associations including CYP2C19 downregulation. We chose to validate CYP2C19 due to its actionability in drug prescribing. Meta-analysis of 16 independent studies demonstrate that CYP2C19 is significantly downregulated to 46% in NASH, to 58% in high NAS, and to 43% in severe fibrosis. Our data demonstrate the downregulation of CYP2C19 in NAFLD which supports developing personalized medicine approaches for drugs sensitive to metabolism by the CYP2C19 enzyme.
Tirzepatide, a dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonist, shows a remarkable ability to lower blood glucose, enabling many patients with long-standing type 2 ...diabetes to achieve normoglycaemia. We aimed to understand the physiological mechanisms underlying the action of tirzepatide in type 2 diabetes.
This multicentre, randomised, double-blind, parallel-arm, phase 1 study was done at two centres in Germany. Eligible patients were aged 20-74 years, had type 2 diabetes for at least 6 months, and were being treated with lifestyle advice and stable doses of metformin, with or without one additional stable dose of another oral antihyperglycaemic medicine, 3 months before study entry. Via a randomisation table, patients were randomly assigned (3:3:2) to subcutaneously receive either tirzepatide 15 mg, semaglutide 1 mg, or placebo once per week. Endpoint measurements were done at baseline and the last week of therapy (week 28). The primary endpoint was the effect of tirzepatide versus placebo on the change in clamp disposition index (combining measures of insulin secretion and sensitivity) from baseline to week 28 of treatment and was analysed in the pharmacodynamic analysis set, which comprised all randomly assigned participants who received at least one dose of a study drug and had evaluable pharmacodynamic data. Safety was analysed in the safety population, which comprised all randomly assigned participants who received at least one dose of a study drug. Secondary endpoints included the effect of tirzepatide versus semaglutide on the change in clamp disposition index from baseline to week 28 of treatment, glucose control, total insulin secretion rate, M value (insulin sensitivity), and fasting and postprandial glucagon concentrations. Exploratory endpoints included the change in fasting and postprandial insulin concentrations. This study is registered with ClinicalTrials.gov, NCT03951753, and is complete.
Between June 28, 2019, and April 8, 2021, we screened 184 individuals and enrolled 117 participants, all of whom were included in the safety population (45 in the tirzepatide 15 mg group, 44 in the semaglutide 1 mg group, and 28 in the placebo group). Because of discontinuations and exclusions due to missing or unevaluable data, 39 patients in each treatment group and 24 patients in the placebo group comprised the pharmacodynamic analysis set. With tirzepatide, the clamp disposition index increased from a least squares mean of 0·3 pmol m
L min
kg
(SE 0·03) at baseline by 1·9 pmol m
L min
kg
(0·16) to total 2·3 pmol m
L min
kg
(SE 0·16) at week 28 and, with placebo, the clamp disposition index did not change much from baseline (least squares mean at baseline 0·4 pmol m
L min
kg
SE 0·04; change from baseline 0·0 pmol m
L min
kg
0·03; least squares mean at week 28 0·3 SE 0·03; estimated treatment difference ETD tirzepatide vs placebo 1·92 95% CI 1·59-2·24; p<0·0001). The improvement with tirzepatide in clamp disposition index was significantly greater than with semaglutide (ETD 0·84 pmol m
L min
kg
95% CI 0·46-1·21). This result reflected significant improvements in total insulin secretion rate (ETD 102·09 pmol min
m
51·84-152·33) and insulin sensitivity (ETD 1·52 mg min
kg
0·53-2·52) for tirzepatide versus semaglutide. On meal tolerance testing, tirzepatide significantly reduced glucose excursions (lower insulin and glucagon concentrations) compared with placebo, with effects on these variables being greater than with semaglutide. The safety profiles of tirzepatide and semaglutide were similar, with gastrointestinal adverse events being the most common (11 24%, 13 30%, and seven 25% with nausea; nine 20%, 13 30%, and six 21% with diarrhoea; and three 7%, five 11%, and one 4% with vomiting, for tirzepatide, semaglutide, and placebo, respectively). There were no deaths.
The glycaemic efficacy of GIP/GLP-1 receptor agonist tirzepatide in type 2 diabetes results from concurrent improvements in key components of diabetes pathophysiology, namely β-cell function, insulin sensitivity, and glucagon secretion. These effects were large and help to explain the remarkable glucose-lowering ability of tirzepatide seen in phase 3 studies.
Eli Lilly.
Treating hyperglycaemia and obesity in individuals with type 2 diabetes using multi-receptor agonists can improve short-term and long-term outcomes. LY3437943 is a single peptide with agonist ...activity for glucagon, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide 1 (GLP-1) receptors that is currently in development for the treatment of type 2 diabetes and for the treatment of obesity and associated comorbidities. We investigated the safety, pharmacokinetics, and pharmacodynamics of multiple weekly doses of LY3437943 in people with type 2 diabetes in a 12-week study.
In this phase 1b, proof-of-concept, double-blind, placebo-controlled, randomised, multiple-ascending dose trial, adults (aged 20–70 years) with type 2 diabetes for at least 3 months, a glycated haemoglobin A1c (HbA1c) value of 7·0–10·5%, body-mass index of 23–50 kg/m2, and stable bodyweight (<5% change in previous 3 months) were recruited at four centres in the USA. Using an interactive web-response system, participants were randomly assigned to receive once-weekly subcutaneous injections of LY3437943, placebo, or dulaglutide 1·5 mg over a 12-week period. Five ascending dose cohorts were studied, with randomisation in each cohort such that a minimum of nine participants received LY3437943, three received placebo, and one received dulaglutide 1·5 mg within each cohort. The top doses in the two highest dose cohorts were attained via stepwise dose escalations. The primary outcome was to investigate the safety and tolerability of LY3437943, and characterising the pharmacodynamics and pharmacokinetics were secondary outcomes. Safety was analysed in all participants who received at least one dose of study drug, and pharmacodynamics and pharmacokinetics in all participants who received at least one dose of study drug and had evaluable data. This trial is registered at ClinicalTrials.gov, NCT04143802.
Between Dec 18, 2019, and Dec 28, 2020, 210 people were screened, of whom 72 were enrolled, received at least one dose of study drug, and were included in safety analyses. 15 participants had placebo, five had dulaglutide 1·5 mg and, for LY3437943, nine had 0·5 mg, nine had 1·5 mg, 11 had 3 mg, 11 had 3/6 mg, and 12 had 3/6/9/12 mg. 29 participants discontinued the study prematurely. Treatment-emergent adverse events were reported by 33 (63%), three (60%), and eight (54%) participants who received LY3437943, dulaglutide 1·5 mg, and placebo, respectively, with gastrointestinal disorders being the most frequently reported treatment-emergent adverse events. The pharmacokinetics of LY3437943 were dose proportional and its half-life was approximately 6 days. At week 12, placebo-adjusted mean daily plasma glucose significantly decreased from baseline at the three highest dose LY3437943 groups (least-squares mean difference –2·8 mmol/L 90% CI –4·63 to –0·94 for 3 mg; –3·1 mmol/L –4·91 to –1·22 for 3/6 mg; and –2·9 mmol/L –4·70 to –1·01 for 3/6/9/12 mg). Placebo-adjusted sHbA1c also decreased significantly in the three highest dose groups (–1·4% 90% CI –2·17 to –0·56 for 3 mg; –1·6% –2·37 to –0·75 for 3/6 mg; and –1·2% –2·05 to –0·45 for 3/6/9/12 mg). Placebo-adjusted bodyweight reduction with LY3437943 appeared to be dose dependent (up to –8·96 kg 90% CI –11·16 to –6·75 in the 3/6/9/12 mg group).
In this early phase study, LY3437943 showed an acceptable safety profile, and its pharmacokinetics suggest suitability for once-weekly dosing. This finding, together with the pharmacodynamic findings of robust reductions in glucose and bodyweight, provides support for phase 2 development.
Eli Lilly and Company.
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