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We have identified a series of novel insulin receptor partial agonists (IRPAs) with a potential to mitigate the risk of hypoglycemia associated with the use of insulin as an antidiabetic treatment. These molecules were designed as dimers of native insulin connected via chemical linkers of variable lengths with optional capping groups at the N-terminals of insulin chains. Depending on the structure, the maximal activation level (%Max) varied in the range of ∼20-70% of native insulin, and EC 50 values remained in sub-nM range. Studies in minipig and dog demonstrated that IRPAs had sufficient efficacy to normalize plasma glucose levels in diabetes, while providing reduction of hypoglycemia risk. IRPAs had a prolonged duration of action, potentially making them suitable for once-daily dosing. Two lead compounds with %Max values of 30 and 40% relative to native insulin were selected for follow up studies in the clinic.

Insulin analogs have been developed to treat diabetes with focus primarily on improving the time action profile without affecting ligand-receptor interaction or functional selectivity. As a result, inherent liabilities (e.g. hypoglycemia) of injectable insulin continue to limit the true therapeutic potential of related agents. Insulin dimers were synthesized to investigate whether partial agonism of the insulin receptor (IR) tyrosine kinase is achievable, and to explore the potential for tissue-selective systemic insulin pharmacology. The insulin dimers induced distinct IR conformational changes compared to native monomeric insulin and substrate phosphorylation assays demonstrated partial agonism. Structurally distinct dimers with differences in conjugation sites and linkers were prepared to deliver desirable IR partial agonist (IRPA). Systemic infusions of a B29-B29 dimer in vivo revealed sharp differences compared to native insulin. Suppression of hepatic glucose production and lipolysis were like that attained with regular insulin, albeit with a distinctly shallower dose-response. In contrast, there was highly attenuated stimulation of glucose uptake into muscle. Mechanistic studies indicated that IRPAs exploit tissue differences in receptor density and have additional distinctions pertaining to drug clearance and distribution. The hepato-adipose selective action of IRPAs is a potentially safer approach for treatment of diabetes., (© 2022. The Author(s).)

Aims/hypothesis: The risk for coronary artery disease (CAD) is substantially increased in type 1 diabetes and it has been postulated that insulin resistance may contribute to this risk. The current study measured insulin resistance in type 1 diabetes with vs without CAD and with a focus upon skeletal muscle, to test the hypothesis that insulin resistance is more severe in participants who have type 1 diabetes and CAD. Additionally, in type 1 diabetes, we examined the hypothesis that insulin resistance is more severe in soleus (an oxidative type muscle) vs tibialis anterior (a more glycolytic type of muscle)., Methods: Insulin resistance was measured in participants with type 1 diabetes with (n = 9, CAD+) and without CAD (n = 10, CAD-) using euglycaemic insulin infusions combined with positron emission tomography (PET) imaging of [ 18 F]fluorodeoxyglucose (FDG) uptake into soleus and tibialis anterior skeletal muscles. Coronary artery calcium (CAC) score was quantified by electron beam tomography., Results: CAD+ participants with type 1 diabetes had a >100-fold higher CAC score than did CAD- participants with type 1 diabetes but groups did not differ in HbA 1c or insulin dose. During clamp studies, CAD+ and CAD- groups had similar glucose disposal but were insulin resistant compared with historical non-diabetic participants (n = 13). FDG uptake by soleus muscle was similarly reduced, overall, in individuals with type 1 diabetes with or without CAD compared with non-diabetic individuals. However, FDG uptake by tibialis anterior muscle was not reduced in CAD- participants with type 1 diabetes while in CAD+ participants with type 1 diabetes it was 75% greater (p < 0.01). Across all participants with type 1 diabetes, FDG uptake by tibialis anterior muscle correlated positively with CAC severity., Conclusions/interpretation: Our study confirms that systemic and skeletal muscle-specific insulin resistance is seen in type 1 diabetes but found that it does not appear to be more severe in the presence of CAD. There were, however, sharp differences between soleus and tibialis anterior muscles in type 1 diabetes: while insulin resistance was clearly manifest in soleus muscle, and was of equal severity in CAD+ and CAD- participants, tibialis anterior did not suggest insulin resistance in participants with type 1 diabetes, as FDG uptake by tibialis anterior correlated positively with CAC severity and was significantly increased in participants with type 1 diabetes and clinical CAD. Graphical abstract.

Metabolic dysregulation and mitochondrial dysfunction are important features of acute and chronic tissue injury across species, and human genetics and preclinical data suggest that the master metabolic regulator 5'-adenosine monophosphate-activated protein kinase (AMPK) may be an effective therapeutic target for chronic kidney disease (CKD). We have recently disclosed a pan-AMPK activator, MK-8722, that was shown to have beneficial effects in preclinical models. In this study we investigated the effects of MK-8722 in a progressive rat model of diabetic nephropathy to determine whether activation of AMPK would be of therapeutic benefit. We found that MK-8722 administration in a therapeutic paradigm is profoundly renoprotective, as demonstrated by a reduction in proteinuria (63% decrease in MK-8722 10 mg/kg per day compared with vehicle group) and a significant improvement in glomerular filtration rate (779 and 430 μ l/min per gram kidney weight in MK-8722 10 mg/kg per day and vehicle group, respectively), as well as improvements in kidney fibrosis. We provide evidence that the therapeutic effects of MK-8722 may be mediated by modulation of renal mitochondrial quality control as well by attenuating fibrotic and lipotoxic mechanisms in kidney cells. MK-8722 (10 mg/kg per day compared with vehicle group) achieved modest blood pressure reduction (10 mmHg lower for mean blood pressure) and significant metabolic improvements (decreased plasma glucose, triglyceride, and body weight) that could contribute to renoprotection. These data further validate the concept that targeting metabolic dysregulation in CKD could be a potential therapeutic approach. SIGNIFICANCE STATEMENT: We demonstrate in the present study that the pharmacological activation of AMPK using a small-molecule agent provided renoprotection and improved systemic and cellular metabolism. We further indicate that modulation of renal mitochondrial quality control probably contributed to renoprotection and was distinct from the effects of enalapril. Our findings suggest that improving renal mitochondrial biogenesis and function and attenuating fibrosis and lipotoxicity by targeting key metabolic nodes could be a potential therapeutic approach in management of CKD that could complement the current standard of care., (Copyright © 2019 by The American Society for Pharmacology and Experimental Therapeutics.)

Ceramides contribute to the lipotoxicity that underlies diabetes, hepatic steatosis, and heart disease. By genetically engineering mice, we deleted the enzyme dihydroceramide desaturase 1 (DES1), which normally inserts a conserved double bond into the backbone of ceramides and other predominant sphingolipids. Ablation of DES1 from whole animals or tissue-specific deletion in the liver and/or adipose tissue resolved hepatic steatosis and insulin resistance in mice caused by leptin deficiency or obesogenic diets. Mechanistic studies revealed ceramide actions that promoted lipid uptake and storage and impaired glucose utilization, none of which could be recapitulated by (dihydro)ceramides that lacked the critical double bond. These studies suggest that inhibition of DES1 may provide a means of treating hepatic steatosis and metabolic disorders., (Copyright © 2019, American Association for the Advancement of Science.)

The regulation of nutrient homeostasis, i.e., the ability to transition between fasted and fed states, is fundamental in maintaining health. Since food is typically consumed over limited (anabolic) periods, dietary components must be processed and stored to counterbalance the catabolic stress that occurs between meals. Herein, we contrast tissue- and pathway-specific metabolic activity in fasted and fed states. We demonstrate that knowledge of biochemical kinetics that is obtained from opposite ends of the energetic spectrum can allow mechanism-based differentiation of healthy and disease phenotypes. Rat models of type 1 and type 2 diabetes serve as case studies for probing spatial and temporal patterns of metabolic activity via [ 2 H]water labeling. Experimental designs that capture integrative whole body metabolism, including meal-induced substrate partitioning, can support an array of research surrounding metabolic disease; the relative simplicity of the approach that is discussed here should enable routine applications in preclinical models.

Physical activity promotes metabolic and cardiovascular health benefits that derive in part from the transcriptional responses to exercise that occur within skeletal muscle and other organs. There is interest in discovering a pharmacologic exercise mimetic that could imbue wellness and alleviate disease burden. However, the molecular physiology by which exercise signals the transcriptional response is highly complex, making it challenging to identify a single target for pharmacological mimicry. The current studies evaluated the transcriptome responses in skeletal muscle, heart, liver, and white and brown adipose to novel small molecule activators of AMPK (pan-activators for all AMPK isoforms) compared to that of exercise. A striking level of congruence between exercise and pharmacological AMPK activation was observed across the induced transcriptome of these five tissues. However, differences in acute metabolic response between exercise and pharmacologic AMPK activation were observed, notably for acute glycogen balances and related to the energy expenditure induced by exercise but not pharmacologic AMPK activation. Nevertheless, intervention with repeated daily administration of short-acting activation of AMPK was found to mitigate hyperglycemia and hyperinsulinemia in four rodent models of metabolic disease and without the cardiac glycogen accretion noted with sustained pharmacologic AMPK activation. These findings affirm that activation of AMPK is a key node governing exercise mediated transcription and is an attractive target as an exercise mimetic., Competing Interests: All authors are or were employees of Merck & Co., Inc., Kenilworth, NJ, USA, and may own shares of company stock. Merck & Co., Inc., Kenilworth, NJ, USA, provisional patent applications for LA1, LA2, SA1 and SA2 and related AMPK activators were filed on 23 February 2012 (WO2012116145; Novel Cyclic Azabenzimidazole derivatives useful as anti-diabetic agents). All of the authors employed by Merck & Co., Inc., Kenilworth, NJ, USA, have a potential conflict of interest. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

The goal of this investigation was to examine clinical translation of glucose responsiveness of MK-2640, which is a novel insulin saccharide conjugate that can bind the insulin receptor or mannose receptor C type 1 (MRC1), the latter dependent upon glucose concentration. In a rising dose study in 36 healthy adults under euglycemic clamp conditions, rising exposures revealed saturation of MK-2640 clearance, likely due to saturation of clearance by MRC1. Potency of MK-2640 was ~25-fold reduced relative to regular human insulin. In a randomized, 2-period crossover trial in 16 subjects with type 1 diabetes mellitus to evaluate glucose-responsiveness of i.v. administered MK-2640, we were unable to demonstrate a glucose-dependent change in MK-2640 clearance, although a significant glucose-dependent augmentation of glucose infusion rate was observed. These pharmacokinetic (PK) and pharmacodynamic (PD) data provide crucial insights into next steps for developing an insulin saccharide conjugate as a clinically effective glucose-responsive insulin analog., (© 2018 American Society for Clinical Pharmacology and Therapeutics.)

Numerous studies have implicated dyslipidemia as a key factor in mediating insulin resistance. Ceramides have received special attention since their levels are inversely associated with normal insulin signaling and positively associated with factors that are involved in cardiometabolic disease. Despite the growing literature surrounding ceramide biology, there are limited data regarding the activity of ceramide synthesis and turnover in vivo. Herein, we demonstrate the ability to measure ceramide kinetics by coupling the administration of [ 2 H]water with LC-MS/MS analyses. As a "proof-of-concept" we determined the effect of a diet-induced alteration on ceramide flux; studies also examined the effect of myriocin (a known inhibitor of serine palmitoyltransferase, the first step in sphingosine biosynthesis). Our data suggest that one can estimate ceramide synthesis and draw conclusions regarding the source of fatty acids; we discuss caveats in regards to method development in this area.

An increased contribution of de novo lipogenesis (DNL) may play a role in cases of dyslipidemia and adipose accretion; this suggests that inhibition of fatty acid synthesis may affect clinical phenotypes. Since it is not clear whether modulation of one step in the lipogenic pathway is more important than another, the use of tracer methods can provide a deeper level of insight regarding the control of metabolic activity. Although [ 2 H]water is generally considered a reliable tracer for quantifying DNL in vivo (it yields a homogenous and quantifiable precursor labeling), the relatively long half-life of body water is thought to limit the ability of performing repeat studies in the same subjects; this can create a bottleneck in the development and evaluation of novel therapeutics for inhibiting DNL. Herein, we demonstrate the ability to perform back-to-back studies of DNL using [ 2 H]water. However, this work uncovered special circumstances that affect the data interpretation, i.e., it is possible to obtain seemingly negative values for DNL. Using a rodent model, we have identified a physiological mechanism that explains the data. We show that one can use [ 2 H]water to test inhibitors of DNL by performing back-to-back studies in higher species [i.e., treat nonhuman primates with platensimycin, an inhibitor of fatty acid synthase]; studies also demonstrate the unsuitability of [ 13 C]acetate.

Insulin-induced hypoglycemia in diabetes is associated with impaired glucagon secretion. In this study, we tested whether stimulation of GPR119, a G-protein-coupled receptor expressed in pancreatic islet as well as enteroendocrine cells and previously shown to stimulate insulin and incretin secretion, might enhance glucagon secretion during hypoglycemia. In the study, GPR119 agonists were applied to isolated islets or perfused pancreata to assess insulin and glucagon secretion during hypoglycemic or hyperglycemic conditions. Insulin infusion hypoglycemic clamps were performed with or without GPR119 agonist pretreatment to assess glucagon counterregulation in healthy and streptozotocin (STZ)-induced diabetic rats, including those exposed to recurrent bouts of insulin-induced hypoglycemia that leads to suppression of hypoglycemia-induced glucagon release. Hypoglycemic clamp studies were also conducted in GPR119 knockout (KO) mice to evaluate whether the pharmacological stimulatory actions of GPR119 agonists on glucagon secretion during hypoglycemia were an on-target effect. The results revealed that GPR119 agonist-treated pancreata or cultured islets had increased glucagon secretion during low glucose perfusion. In vivo, GPR119 agonists also significantly increased glucagon secretion during hypoglycemia in healthy and STZ-diabetic rats, a response that was absent in GPR119 KO mice. In addition, impaired glucagon counterregulatory responses were restored by a GPR119 agonist in STZ-diabetic rats that were exposed to antecedent bouts of hypoglycemia. Thus, GPR119 agonists have the ability to pharmacologically augment glucagon secretion, specifically in response to hypoglycemia in diabetic rodents. Whether this effect might serve to diminish the occurrence and severity of iatrogenic hypoglycemia during intensive insulin therapy in patients with diabetes remains to be established., (© 2018 by the American Diabetes Association.)

Oxyntomodulin (OXM), an enteroendocrine hormone, causes appetite suppression, increased energy expenditure, and weight loss in obese humans via activation of GLP-1 and glucagon receptors. However, the effects of OXM on glucose homeostasis remain ill defined. To address this gap, we evaluated the effects of an i.v. infusion of native OXM on insulin secretion rates (ISRs) and glycemic excursion in a graded glucose infusion (GGI) procedure in two separate randomized, placebo (PBO)-controlled, single-dose crossover trials in 12 overweight and obese subjects without diabetes and in 12 obese subjects with type 2 diabetes mellitus (T2DM), using the GLP-1 analog liraglutide (LIRA) as a comparator in T2DM. In both groups, in the GGI, 3.0 pmol/kg/min of OXM significantly increased ISR and blunted glycemic excursion relative to PBO. In T2DM, the effects of OXM were comparable to those of LIRA, including restoration of β-cell glucose responsiveness to that of nonobese subjects without diabetes. Our findings indicate that native OXM significantly augments glucose-dependent insulin secretion acutely in obese subjects with and without diabetes, with effects comparable to pharmacologic GLP-1 receptor activation and independent of weight loss. Native OXM has potential to improve hyperglycemia via complementary and independent induction of insulin secretion and weight loss., (© 2018 by the American Diabetes Association.)

We evaluated the hepatic and nonhepatic responses to glucose-responsive insulin (GRI). Eight dogs received GRI or regular human insulin (HI) in random order. A primed, continuous intravenous infusion of [3- 3 H]glucose began at -120 min. Basal sampling (-30 to 0 min) was followed by two study periods (150 min each), clamp period 1 (P1) and clamp period 2 (P2). At 0 min, somatostatin and GRI (36 ± 3 pmol/kg/min) or HI (1.8 pmol/kg/min) were infused intravenously; basal glucagon was replaced intraportally. Glucose was infused intravenously to clamp plasma glucose at 80 mg/dL (P1) and 240 mg/dL (P2). Whole-body insulin clearance and insulin concentrations were not different in P1 versus P2 with HI, but whole-body insulin clearance was 23% higher and arterial insulin 16% lower in P1 versus P2 with GRI. Net hepatic glucose output was similar between treatments in P1. In P2, both treatments induced net hepatic glucose uptake (HGU) (HI mean ± SEM 2.1 ± 0.5 vs. 3.3 ± 0.4 GRI mg/kg/min). Nonhepatic glucose uptake in P1 and P2, respectively, differed between treatments (2.6 ± 0.3 and 7.4 ± 0.6 mg/kg/min with HI vs. 2.0 ± 0.2 and 8.1 ± 0.8 mg/kg/min with GRI). Thus, glycemia affected GRI but not HI clearance, with resultant differential effects on HGU and nonHGU. GRI holds promise for decreasing hypoglycemia risk while enhancing glucose uptake under hyperglycemic conditions., (© 2018 by the American Diabetes Association.)

Aims/hypothesis: In this prospective case-control study we tested the hypothesis that, while long-term improvements in insulin sensitivity (S I ) accompanying weight loss after Roux-en-Y gastric bypass (RYGB) would be similar in obese individuals with and without type 2 diabetes mellitus, stimulated-islet-cell insulin responses would differ, increasing (recovering) in those with diabetes but decreasing in those without. We investigated whether these changes would occur in conjunction with favourable alterations in meal-related gut hormone secretion and insulin processing., Methods: Forty participants with type 2 diabetes and 22 participants without diabetes from the Longitudinal Assessment of Bariatric Surgery (LABS-2) study were enrolled in a separate, longitudinal cohort (LABS-3 Diabetes) to examine the mechanisms of postsurgical diabetes improvement. Study procedures included measures of S I , islet secretory response and gastrointestinal hormone secretion after both intravenous glucose (frequently-sampled IVGTT [FSIVGTT]) and a mixed meal (MM) prior to and up to 24 months after RYGB., Results: Postoperatively, weight loss and S I - FSIVGTT improvement was similar in both groups, whereas the acute insulin response to glucose (AIRglu) decreased in the non-diabetic participants and increased in the participants with type 2 diabetes. The resulting disposition indices (DI FSIVGTT ) increased by three- to ninefold in both groups. In contrast, during the MM, total insulin responsiveness did not significantly change in either group despite durable increases of up to eightfold in postprandial glucagon-like peptide 1 levels, and S I-MM and DI MM increased only in the diabetes group. Peak postprandial glucagon levels increased in both groups., Conclusions/interpretation: For up to 2 years following RYGB, obese participants without diabetes showed improvements in DI that approach population norms. Those with type 2 diabetes recovered islet-cell insulin secretion response yet continued to manifest abnormal insulin processing, with DI values that remained well below population norms. These data suggest that, rather than waiting for lifestyle or medical failure, RYGB is ideally considered before, or as soon as possible after, onset of type 2 diabetes., Trial Registration: ClinicalTrials.gov NCT00433810.

Sitagliptin, a dipeptidyl peptidase-IV inhibitor (DPP-4), sustains activity of the incretin hormones GLP-1 and GIP and improves hyperglycemia in Type 2 diabetes mellitus (T2DM). It has however proven challenging to quantify the effect of sitagliptin on rates of insulin secretion (ISR) during a prandial challenge. The tight feedback governance of ISR by plasma glucose means that in the face of treatment-related lowering of postprandial glycemia, corresponding stimulation of ISR is lessened. We postulated that sustaining a stable level of moderate hyperglycemia before and during a meal challenge (MC) would be a platform that enables greater clarity to assess the effect of sitagliptin on ISR and an approach that could be valuable to evaluate novel targets that increase insulin secretion directly and by augmenting incretins. A hyperglycemic clamp (HGC) at 160 mg/dl was conducted in 12 healthy volunteers (without diabetes) for 6 h; 3 h into the HGC, MC was administered while maintaining stable hyperglycemia of the HGC for an additional 3 h. Modeling of C-peptide response was used to calculate ISR. In crossover design of three periods (sitagliptin twice and placebo once), the effect of sitagliptin vs. placebo on ISR and the reproducibility of the response to sitagliptin were assessed. Sitagliptin increased ISR compared with placebo by 50% and 20% during the HGC alone and the HGC-MC phases, respectively ( P < 0.001 for both). There was an associated significant treatment-based increase in circulating insulin, as well as active levels of GLP-1. Robust reproducibility of the sitagliptin-mediated ISR response was observed; the intraclass correlation value was 0.94. The findings delineate the effect of sitagliptin to stimulate insulin secretion, and these benchmark data also demonstrate that an HGC-MC can be a useful platform for interrogating therapeutic targets that could potentially modulate ISR via direct action on beta-cells as well as by augmenting release or action of incretins.

Insulin has a narrow therapeutic index, reflected in a small margin between a dose that achieves good glycemic control and one that causes hypoglycemia. Once injected, the clearance of exogenous insulin is invariant regardless of blood glucose, aggravating the potential to cause hypoglycemia. We sought to create a "smart" insulin, one that can alter insulin clearance and hence insulin action in response to blood glucose, mitigating risk for hypoglycemia. The approach added saccharide units to insulin to create insulin analogs with affinity for both the insulin receptor (IR) and mannose receptor C-type 1 (MR), which functions to clear endogenous mannosylated proteins, a principle used to endow insulin analogs with glucose responsivity. Iteration of these efforts culminated in the discovery of MK-2640, and its in vitro and in vivo preclinical properties are detailed in this report. In glucose clamp experiments conducted in healthy dogs, as plasma glucose was lowered stepwise from 280 mg/dL to 80 mg/dL, progressively more MK-2640 was cleared via MR, reducing by ∼30% its availability for binding to the IR. In dose escalations studies in diabetic minipigs, a higher therapeutic index for MK-2640 (threefold) was observed versus regular insulin (1.3-fold)., (© 2017 by the American Diabetes Association.)

Hypoglycemia is commonly associated with insulin therapy, limiting both its safety and efficacy. The concept of modifying insulin to render its glucose-responsive release from an injection depot (of an insulin complexed exogenously with a recombinant lectin) was proposed approximately 4 decades ago but has been challenging to achieve. Data presented here demonstrate that mannosylated insulin analogs can undergo an additional route of clearance as result of their interaction with endogenous mannose receptor (MR), and this can occur in a glucose-dependent fashion, with increased binding to MR at low glucose. Yet, these analogs retain capacity for binding to the insulin receptor (IR). When the blood glucose level is elevated, as in individuals with diabetes mellitus, MR binding diminishes due to glucose competition, leading to reduced MR-mediated clearance and increased partitioning for IR binding and consequent glucose lowering. These studies demonstrate that a glucose-dependent locus of insulin clearance and, hence, insulin action can be achieved by targeting MR and IR concurrently.

Drug discovery and development efforts are largely based around a common expectation, namely, that direct or indirect action on a cellular process (e.g., statin-mediated enzyme inhibition or insulin-stimulated receptor activation) will have a beneficial impact on physiologic homeostasis. To expand on this, one could argue that virtually all pharmacologic interventions attempt to influence the flow of "traffic" in a biochemical network, irrespective of disease or modality. Since stable isotope tracer kinetic methods provide a measure of traffic flow (i.e., metabolic flux), their inclusion in study designs can yield novel information regarding pathway biology; the application of such methods requires the integration of knowledge in physiology, analytical chemistry, and mathematical modeling. Herein, we review the fundamental concepts that surround the use of tracer kinetics, define basic terms, and outline guiding principles via theoretical and experimental problems. Specifically, one needs to 1) recognize the types of biochemical events that change isotopic enrichments, 2) appreciate the distinction between fractional turnover and flux rate, and 3) be aware of the subtle differences between tracer kinetics and pharmacokinetics. We hope investigators can use the framework presented here to develop applications that address their specific questions surrounding biochemical flux, and thereby gain insight into the pathophysiology of disease states, and examine pharmacodynamic mechanisms., (Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.)

Multiple integrins have been implicated in modulating renal function. Modulation of integrin function can lead to pathophysiological processes associated with diabetic nephropathy such as alterations in the glomerular filtration barrier and kidney fibrosis. The complexity of these pathophysiological changes implies that multiple integrin subtypes might need to be targeted to ameliorate the progression of renal disease. To address this hypothesis, we investigated the effects of MK-0429, a compound that was originally developed as an αvβ3 inhibitor for the treatment of osteoporosis, on renal function and fibrosis. We demonstrated that MK-0429 is an equipotent pan-inhibitor of multiple av integrins. MK-0429 dose-dependently inhibited podocyte motility and also suppressed TGF-β-induced fibrosis marker gene expression in kidney fibroblasts. Moreover, in the obese ZSF1 rat model of diabetic nephropathy, chronic treatment with MK-0429 resulted in significant reduction in proteinuria, kidney fibrosis, and collagen accumulation. In summary, our results suggest that inhibition of multiple integrin subtypes might lead to meaningful impact on proteinuria and renal fibrosis in diabetic nephropathy., (© 2017 The Authors. Pharmacology Research & Perspectives published by John Wiley & Sons Ltd, British Pharmacological Society and American Society for Pharmacology and Experimental Therapeutics.)

5'-Adenosine monophosphate-activated protein kinase (AMPK) is a master regulator of energy homeostasis in eukaryotes. Despite three decades of investigation, the biological roles of AMPK and its potential as a drug target remain incompletely understood, largely because of a lack of optimized pharmacological tools. We developed MK-8722, a potent, direct, allosteric activator of all 12 mammalian AMPK complexes. In rodents and rhesus monkeys, MK-8722-mediated AMPK activation in skeletal muscle induced robust, durable, insulin-independent glucose uptake and glycogen synthesis, with resultant improvements in glycemia and no evidence of hypoglycemia. These effects translated across species, including diabetic rhesus monkeys, but manifested with concomitant cardiac hypertrophy and increased cardiac glycogen without apparent functional sequelae., (Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Inhibiting lipogenesis prevents hepatic steatosis in rodents with insulin resistance. To determine if reducing lipogenesis functions similarly in humans, we developed MK-4074, a liver-specific inhibitor of acetyl-CoA carboxylase (ACC1) and (ACC2), enzymes that produce malonyl-CoA for fatty acid synthesis. MK-4074 administered to subjects with hepatic steatosis for 1 month lowered lipogenesis, increased ketones, and reduced liver triglycerides by 36%. Unexpectedly, MK-4074 increased plasma triglycerides by 200%. To further investigate, mice that lack ACC1 and ACC2 in hepatocytes (ACC dLKO) were generated. Deletion of ACCs decreased polyunsaturated fatty acid (PUFA) concentrations in liver due to reduced malonyl-CoA, which is required for elongation of essential fatty acids. PUFA deficiency induced SREBP-1c, which increased GPAT1 expression and VLDL secretion. PUFA supplementation or siRNA-mediated knockdown of GPAT1 normalized plasma triglycerides. Thus, inhibiting lipogenesis in humans reduced hepatic steatosis, but inhibiting ACC resulted in hypertriglyceridemia due to activation of SREBP-1c and increased VLDL secretion., (Copyright © 2017 Elsevier Inc. All rights reserved.)

GPR40 and GPR120 are fatty acid sensors that play important roles in glucose and energy homeostasis. GPR40 potentiates glucose-dependent insulin secretion and demonstrated in clinical studies robust glucose lowering in type 2 diabetes. GPR120 improves insulin sensitivity in rodents, albeit its mechanism of action is not fully understood. Here, we postulated that the antidiabetic efficacy of GPR40 could be enhanced by coactivating GPR120. A combination of GPR40 and GPR120 agonists in db / db mice, as well as a single molecule with dual agonist activities, achieved superior glycemic control compared with either monotherapy. Compared with a GPR40 selective agonist, the dual agonist improved insulin sensitivity in ob/ob mice measured by hyperinsulinemic-euglycemic clamp, preserved islet morphology, and increased expression of several key lipolytic genes in adipose tissue of Zucker diabetic fatty rats. Novel insights into the mechanism of action for GPR120 were obtained. Selective GPR120 activation suppressed lipolysis in primary white adipocytes, although this effect was attenuated in adipocytes from obese rats and obese rhesus, and sensitized the antilipolytic effect of insulin in rat and rhesus primary adipocytes. In conclusion, GPR120 agonism enhances insulin action in adipose tissue and yields a synergistic efficacy when combined with GPR40 agonism., (Copyright © 2017 by the American Society for Biochemistry and Molecular Biology, Inc.)

Insulin resistance and diabetes can develop spontaneously with obesity and aging in rhesus monkeys, highly similar to the natural history of obesity, insulin resistance, and progression to type 2 diabetes in humans. The current studies in obese rhesus were undertaken to assess hepatic and adipose contributions to systemic insulin resistance-currently, a gap in our knowledge-and to benchmark the responses to pioglitazone (PIO). A two-step hyperinsulinemic-euglycemic clamp, with tracer-based glucose flux estimates, was used to measure insulin resistance, and in an intervention study was repeated following 6 wk of PIO treatment (3 mg/kg). Compared with lean healthy rhesus, obese rhesus has a 60% reduction of glucose utilization during a high insulin infusion and markedly impaired suppression of lipolysis, which was evident at both low and high insulin infusion. However, obese dysmetabolic rhesus manifests only mild hepatic insulin resistance. Six-week PIO treatment significantly improved skeletal muscle and adipose insulin resistance (by ~50%). These studies strengthen the concept that insulin resistance in obese rhesus closely resembles human insulin resistance and indicate the value of obese rhesus for appraising new insulin-sensitizing therapeutics., (Copyright © 2017 the American Physiological Society.)

Background: Glucose homeostasis improves within days following Roux-en-Y gastric bypass (RYGB) surgery. The dynamic metabolic response to caloric intake following RYGB has been assessed using liquid mixed meal tolerance tests (MMTT). Few studies have evaluated the glycemic and hormonal response to a solid mixed meal in subjects with diabetes prior to, and within the first month following RYGB., Methods: Seventeen women with type 2 diabetes of less than 5 years duration participated. Fasting measures of glucose homeostasis, lipids and gut hormones were obtained pre- and post-surgery. MMTT utilizing a solid 4 oz chocolate pudding performed pre-, 2 and 4 weeks post-surgery. Metabolic response to 4 and 2 oz MMTT assessed in five diabetic subjects not undergoing surgery., Results: Significant reductions in fasting glucose and insulin at 3 days, and in fasting betatrophin, triglycerides and total cholesterol at 2 weeks post-surgery. Hepatic insulin clearance was greater at 3 days post-surgery. Subjects exhibited less hunger and greater feelings of fullness and satisfaction during the MMTT while consuming 52.9 ± 6.5% and 51.0 ± 6.5% of the meal at 2 and 4 weeks post-surgery respectively. At 2 weeks post-surgery, glucose and insulin response to MMTT were improved, with greater GLP-1 and PYY secretion. Improved response to solid MMTT not replicated by consumption of smaller pudding volume in diabetic non-surgical subjects., Conclusions: With a test meal of size and composition representative of the routine diet of post-RYGB subjects, improved glycemic and gut hormone responses occur which cannot be replicated by reducing the size of the MMTT in diabetic subjects not undergoing surgery., Trial Registration: Clinical Trials.gov Identifier: NCT00957957 August 11, 2009.

[This corrects the article DOI: 10.1371/journal.pone.0164133.].

Background: The effect of a weight-loss intervention on the masses of lean tissues and organs in humans is not well known., Objective: We studied the effects of a diet and exercise weight-loss intervention on skeletal muscle (SM) mass and selected organs over 2 y using MRI in overweight adults with type 2 diabetes., Design: Participants were 53 women and 39 men [mean ± SD: age 58 ± 7 y; body mass index (BMI; in kg/m 2 ) 32 ± 3] enrolled in the Look AHEAD (Action for Health in Diabetes) trial and randomly assigned to an intensive lifestyle intervention (ILI) or diabetes support and education (DSE) on whom 2 y of data were collected. MRI-derived measurements of SM, heart, liver, kidney, spleen, and pancreas were acquired., Results: Adjusted for baseline weight, height, age, sex, and ethnicity, the ILI group weighed (mean ± SE) 6.6 ± 0.7 kg less after 1 y and 5.2 ± 0.7 kg less after 2 y, whereas the DSE group did not change significantly (-0.4 ± 0.6 and -1.0 ± 0.7 kg after 1 and 2 y, respectively; P-interaction < 0.001). Total SM decreased in both groups during year 1 (-1.4 ± 0.2 kg; P < 0.001) with appendicular SM regained during year 2. Liver and spleen masses decreased in the ILI group (-0.12 ± 0.02 and -0.006 ± 0.003 kg, respectively) but were unchanged in the DSE group (0.00 ± 0.02 and 0.004 ± 0.003 kg, respectively). Kidney mass decreased by 0.013 ± 0.003 kg (P < 0.001) over 2 y in both groups., Conclusions: Decreases in liver (in Caucasians but not African Americans) and spleen were detected after a 6.2-kg weight reduction compared with a control group. SM and kidney mass decreased in both groups. Appendicular SM was regained during the second year whereas trunk SM was not. No evidence of a disproportionate loss of high-metabolic rate organs (heart, liver, kidney, spleen) compared with SM was found., (© 2017 American Society for Nutrition.)

Aberrant regulation of glucose production makes a critical contribution to the impaired glycemic control that is observed in type 2 diabetes. Although isotopic tracer methods have proven to be informative in quantifying the magnitude of such alterations, it is presumed that one must rely on venous access to administer glucose tracers which therein presents obstacles for the routine application of tracer methods in rodent models. Since intraperitoneal injections are readily used to deliver glucose challenges and/or dose potential therapeutics, we hypothesized that this route could also be used to administer a glucose tracer. The ability to then reliably estimate glucose flux would require attention toward setting a schedule for collecting samples and choosing a distribution volume. For example, glucose production can be calculated by multiplying the fractional turnover rate by the pool size. We have taken a step-wise approach to examine the potential of using an intraperitoneal tracer administration in rat and mouse models. First, we compared the kinetics of [U- 13 C]glucose following either an intravenous or an intraperitoneal injection. Second, we tested whether the intraperitoneal method could detect a pharmacological manipulation of glucose production. Finally, we contrasted a potential application of the intraperitoneal method against the glucose-insulin clamp. We conclude that it is possible to 1) quantify glucose production using an intraperitoneal injection of tracer and 2) derive a "glucose production index" by coupling estimates of basal glucose production with measurements of fasting insulin concentration; this yields a proxy for clamp-derived assessments of insulin sensitivity of endogenous production., (Copyright © 2016 the American Physiological Society.)

Mutations of the AMP-activated kinase gamma 2 subunit (AMPKγ2), N488I (AMPKγ2 NI ) and R531G (AMPKγ2 RG ), are associated with Wolff-Parkinson-White (WPW) syndrome, a cardiac disorder characterized by ventricular pre-excitation in humans. Cardiac-specific transgenic overexpression of human AMPKγ2 NI or AMPKγ2 RG leads to constitutive AMPK activation and the WPW phenotype in mice. However, overexpression of these mutant proteins also caused profound, non-physiological increase in cardiac glycogen, which might abnormally alter the true phenotype. To investigate whether physiological levels of AMPKγ2 NI or AMPKγ2 RG mutation cause WPW syndrome and metabolic changes in other organs, we generated two knock-in mouse lines on the C57BL/6N background harboring mutations of human AMPKγ2 NI and AMPKγ2 RG , respectively. Similar to the reported phenotypes of mice overexpressing AMPKγ2 NI or AMPKγ2 RG in the heart, both lines developed WPW syndrome and cardiac hypertrophy; however, these effects were independent of cardiac glycogen accumulation. Compared with AMPKγ2 WT mice, AMPKγ2 NI and AMPKγ2 RG mice exhibited reduced body weight, fat mass, and liver steatosis when fed with a high fat diet (HFD). Surprisingly, AMPKγ2 RG but not AMPKγ2 NI mice fed with an HFD exhibited severe kidney injury characterized by glycogen accumulation, inflammation, apoptosis, cyst formation, and impaired renal function. These results demonstrate that expression of AMPKγ2 NI and AMPKγ2 RG mutations at physiological levels can induce beneficial metabolic effects but that this is accompanied by WPW syndrome. Our data also reveal an unexpected effect of AMPKγ2 RG in the kidney, linking lifelong constitutive activation of AMPK to a potential risk for kidney dysfunction in the context of an HFD., (© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.)

Objectives: Platensimycin (PTM) is a natural antibiotic produced by Streptomyces platensis that selectively inhibits bacterial and mammalian fatty acid synthase (FAS) without affecting synthesis of other lipids. Recently, we reported that oral administration of PTM in mouse models (db/db and db/+) with high de novo lipogenesis (DNL) tone inhibited DNL and enhanced glucose oxidation, which in turn led to net reduction of liver triglycerides (TG), reduced ambient glucose, and improved insulin sensitivity. The present study was conducted to explore translatability and the therapeutic potential of FAS inhibition for the treatment of diabetes in humans., Methods: We tested PTM in animal models with different DNL tones, i.e. intrinsic synthesis rates, which vary among species and are regulated by nutritional and disease states, and confirmed glucose-lowering efficacy of PTM in lean NHPs with quantitation of liver lipid by MRS imaging. To understand the direct effect of PTM on liver metabolism, we performed ex vivo liver perfusion study to compare FAS inhibitor and carnitine palmitoyltransferase 1 (CPT1) inhibitor., Results: The efficacy of PTM is generally reproduced in preclinical models with DNL tones comparable to humans, including lean and established diet-induced obese (eDIO) mice as well as non-human primates (NHPs). Similar effects of PTM on DNL reduction were observed in lean and type 2 diabetic rhesus and lean cynomolgus monkeys after acute and chronic treatment of PTM. Mechanistically, PTM lowers plasma glucose in part by enhancing hepatic glucose uptake and glycolysis. Teglicar, a CPT1 inhibitor, has similar effects on glucose uptake and glycolysis. In sharp contrast, Teglicar but not PTM significantly increased hepatic TG production, thus caused liver steatosis in eDIO mice., Conclusions: These findings demonstrate unique properties of PTM and provide proof-of-concept of FAS inhibition having potential utility for the treatment of diabetes and related metabolic disorders., Competing Interests: The authors are employees of Merck & Co., Inc. and declare no competing interests. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Objective: Bariatric surgery induces weight loss and improvement of insulin resistance; one aspect of both is an amelioration of hepatic steatosis. This study was undertaken to assess the changes in the hepatic lipidome after duodenal-jejunal bypass (DJB) surgery., Methods: A DJB surgical model was developed and characterized in diet-induced obese mice. In comparison with sham-operated mice, an unbiased lipidomic profiling of hepatic lipids was performed together with measurements of gene expression within key pathways of hepatic lipid metabolism., Results: In the liver of DJB mice, a dramatic reduction (by 77%) in hepatic triacylglycerols was observed. Global lipidomic profiling identified marked decreases of triacylglycerols comprised of medium length fatty acids and with low double bond content. Specific diacylglycerol species were also among the most dramatic decreases in hepatic lipids, whereas lysophosphatidic acids and phosphatidic acids were increased. Expression of fatty acid transporter and lipogenic genes was down-regulated., Conclusions: From in-depth analysis of hepatic lipid composition, specific lipid intermediates were identified that are preferentially changed following DJB surgery. These changes were most likely due to DJB-induced weight loss, and only further studies will be able to distinguish weight loss-dependent from weight loss-independent changes., (© 2016 The Obesity Society.)

The graded glucose infusion (GGI) examines insulin secretory response patterns to continuously escalating glycemia. The current study series sought to more fully appraise its performance characteristics. Key questions addressed were comparison of the GGI to the hyperglycemic clamp (HGC), comparison of insulin secretory response patterns across three volunteer populations known to differ in β-cell function (healthy nonobese, obese nondiabetic, and type 2 diabetic), and characterization of effects of known insulin secretagogues in the context of a GGI. Insulin secretory response was measured as changes in insulin, C-peptide, insulin secretion rates (ISR), and ratio of ISR to prevailing glucose (ISR/G). The GGI correlated well with the HGC (r = 0.72 for ISR/G, P < 0.01). The insulin secretory response in type 2 diabetes (T2DM) was significantly blunted (P < 0.001), whereas it was significantly increased in obese nondiabetics compared with healthy nonobese (P < 0.001). Finally, robust (P < 0.001 over placebo) pharmacological effects were observed in T2DM and healthy nonobese volunteers. Collectively, the findings of this investigational series bolster confidence that the GGI has solid attributes for assessing insulin secretory response to glucose across populations and pharmacology. Notably, the coupling of insulin secretory response to glycemic changes was distinctly and uniformly linear across populations and in the context of insulin secretagogues. (Clinical Trial Registration Nos. NCT00782418, NCT01055340, NCT01373450)., (Copyright © 2016 the American Physiological Society.)

Glucagon and insulin have opposing action in governing glucose homeostasis. In type 2 diabetes mellitus (T2DM), plasma glucagon is characteristically elevated, contributing to increased gluconeogenesis and hyperglycemia. Therefore, glucagon receptor (GCGR) antagonism has been proposed as a pharmacologic approach to treat T2DM. In support of this concept, a potent small-molecule GCGR antagonist (GRA), MK-0893, demonstrated dose-dependent efficacy to reduce hyperglycemia, with an HbA1c reduction of 1.5% at the 80 mg dose for 12 weeks in T2DM. However, GRA treatment was associated with dose-dependent elevation of plasma LDL-cholesterol (LDL-c). The current studies investigated the cause for increased LDL-c. We report findings that link MK-0893 with increased glucagon-like peptide 2 and cholesterol absorption. There was not, however, a GRA-related modulation of cholesterol synthesis. These findings were replicated using structurally diverse GRAs. To examine potential pharmacologic mitigation, coadministration of ezetimibe (a potent inhibitor of cholesterol absorption) in mice abrogated the GRA-associated increase of LDL-c. Although the molecular mechanism is unknown, our results provide a novel finding by which glucagon and, hence, GCGR antagonism govern cholesterol metabolism., (Copyright © 2015 by the American Society for Biochemistry and Molecular Biology, Inc.)

Two groups recently used different tracer methods to quantify liver-specific flux rates. The studies had a similar goal, i.e., to characterize mitochondrial oxidative function. These efforts could have a direct impact on our ability to understand metabolic abnormalities that affect the pathophysiology of fatty liver and allow us to examine mechanisms surrounding potential therapeutic interventions. Briefly, one method couples the continuous infusion of [(13)C]acetate with direct real-time measurements of [(13)C]glutamate labeling in liver; the other method administers [(13)C]propionate, in combination with other tracers, and subsequently measures the (13)C labeling of plasma glucose and/or acetaminophen-glucuronide. It appears that a controversy has arisen, since the respective methods yielded different estimates of the anaplerotic/TCA flux ratio (VANA:VTCA) in "control" subjects, i.e., the [(13)C]acetate- and [(13)C]propionate-derived VANA:VTCA flux ratios appear to be ∼1.4 and ∼5, respectively. While the deep expertise in the respective groups makes it somewhat trivial for each to perform the tracer studies, the data interpretation is inherently difficult. The current perspective was undertaken to examine potential factors that could account for or contribute to the apparent differences. Attention was directed toward 1) matters of practicality, 2) issues surrounding stoichiometry, and 3) hidden assumptions. We believe that the [(13)C]acetate method has certain weaknesses that limit its utility; in contrast, the [(13)C]propionate method likely yields a more correct answer. We hope our discussion will help clarify the differences in the recent reports. Presumably this will be of interest to investigators who are considering tracer-based studies of liver metabolism., (Copyright © 2015 the American Physiological Society.)

Background: Insulin resistance heightens the risk for type 2 diabetes mellitus and cardiovascular disease. Amelioration of insulin resistance may reduce this risk. The thiazolidinedone class of insulin sensitizers improves insulin action in individuals with insulin-resistant diabetes and nondiabetic individuals. However, there are few reports on the time of onset of such effects independent of reversal of glucotoxicity., Objective: The goal of our study was to test whether the thiazolidinedione pioglitazone has prominent early metabolic effects that can be detected in an obese, nondiabetic, insulin-resistant population., Methods: We conducted a randomized, double-blind, placebo-controlled, parallel-group trial in men with nondiabetic insulin resistance using a hyperinsulinemic euglycemic clamp technique (at low and high doses of insulin at 10 and 40 mU/m(2)/min, respectively). The patients were given 30 mg daily oral pioglitazone or placebo for 28 days. Patients underwent a baseline clamp before initiation of treatment, and again at 14 and 28 days of treatment., Results: Compared with placebo, under high-dose hyperinsulinemia, pioglitazone led to significant increases in glucose disposal rates (GDR) of 1.29 mg/kg/min (90% CI, 0.43-2.15; 39%; P=0.008) that were detectable at 2 weeks of treatment and persisted at 4 weeks of treatment. Under low-dose hyperinsulinemia, significant increases in GDR of 0.40 mg/kg/min (90% CI, 0.17-0.62; 95%; P=0.003) were observed at 4 weeks of treatment. These responses were accompanied by robust suppression of free fatty acids under hyperinsulinemic conditions, and by significant increases in circulating basal total adiponectin at 2 and 4 weeks of treatment., Conclusions: Significant changes in insulin action across multiple insulin-sensitive tissues can be detected within 2 weeks of initiation of insulin-sensitizing therapy with pioglitazone in obese patients with nondiabetic insulin resistance. ClinicalTrials.gov identifier: NCT01115712.

The synthesis of various molecules can be estimated by measuring the incorporation of a labeled precursor into a product of interest. Unfortunately, a central problem in many studies has been an inability to estimate the intracellular dilution of the precursor and therein correctly calculate the synthesis of the product; it is generally assumed that measuring the true product labeling is straightforward. We initiated a study to examine liver collagen synthesis and identified an apparent problem with assumptions regarding measurements of the product labeling. Since it is well known that collagen production is relatively slow, we relied on the use of [(2)H]H2O labeling (analogous to a primed infusion) and sampled animals over the course of 16 days. Although the water labeling (the precursor) remained stable and we observed the incorporation of labeled amino acids into collagen, the asymptotic protein labeling was considerably lower than what would be expected based on the precursor labeling. Although this observation is not necessarily surprising (i.e., one might expect that a substantial fraction of the collagen pool would appear "inert" or turn over at a very slow rate), its implications are of interest in certain areas. Herein, we discuss a novel situation in which tracers are used to quantify rates of flux under conditions where a product may not undergo complete replacement. We demonstrate how heterogeneity in the product pool can lead one to the wrong conclusions regarding estimates of flux, and we outline an approach that may help to minimize errors surrounding data interpretation., (Copyright © 2015 the American Physiological Society.)

Background: Glucagon-like peptide 1 (GLP-1) analogs and dipeptidyl peptidase-4 (DPP4) inhibitors are a newer class of antidiabetics named as incretin-based therapy. In addition to the homeostatic control of glucose, the incretin-based therapy has shown beneficial effects on the cardiovascular system in preclinical and clinical studies. However, there is limited information on their renal effects. To this end, we assessed the acute hemodynamic and renal effects of a GLP-1 analog, Liraglutide, and a DPP4 inhibitor, MK-0626., Methods: Experiments were performed in anesthetized male Sprague-Dawley rats. Three ascending doses of Liraglutide (3, 9, and 27 nmol/kg/h) or MK-0626 (1 mg/kg) with or without GLP-1 peptide (2.4, 4.8, or 9.6 pmol/kg/min) were administered. Blood pressure (BP) and heart rate (HR) were recorded from an indwelling catheter. Glomerular filtration rate (GFR) and renal blood flow (RBF) were assessed by inulin and para-aminohippurate clearance, respectively. Renal excretory function was assessed in metabolic studies., Results: Both Liraglutide and MK-0626 plus GLP-1 evoked significant diuretic and natriuretic responses and increased GFR. MK-0626 alone increased RBF. Liraglutide at 27 nmol//kg/h and MK-0626 plus GLP-1 at 9.6 pmol/kg/min also increased HR, whereas BP was not affected., Conclusion: The results of the present study demonstrated that a GLP-1 analog and a DPP4 inhibitor may have beneficial effects on renal sodium and water handling. Additionally, the DPP4 inhibitor, MK-0626, favorably affects renal hemodynamics by increasing RBF. However, exceedingly high levels of GLP-1 receptor agonists may adversely affect the cardiovascular system in acute setting, as demonstrated by an acute increase in HR.

Objective: We aim to characterize the effects on total body fat and distribution of a 1-year intensive lifestyle intervention (ILI) for weight loss in overweight and obese adults with type 2 diabetes and to examine whether changes in adipose tissue (AT) depots were associated with changes in metabolic biomarkers., Research Design and Methods: Participants were 54 females and 38 males (age 57.8 ± 6.7 years [mean ± SD]; BMI 31.7 ± 3.5 kg/m(2)) enrolled in the Look AHEAD (Action for Health in Diabetes) trial randomized to ILI or diabetes support and education (DSE) from whom baseline and 1-year MRI measures of total AT (TAT) and regional (arm, trunk, leg) AT, including subcutaneous AT (SAT), visceral AT (VAT), and intermuscular AT (IMAT), were acquired. We tested whether mean changes in ILI and DSE were equal and, within groups, whether changes were different from zero. Regression models tested whether changes in AT compartments were associated with metabolic variable changes., Results: Body weight changed -0.52 ± 3.62 kg (P = 0.31) in DSE and -7.24 ± 5.40 kg (P < 0.0001) in ILI. Mean ILI changes were different from DSE (P < 0.001 for TAT, SAT, and IMAT and P < 0.01 for VAT in females). Within ILI, SAT and VAT decreased in males and females (P < 0.0001), but IMAT was unchanged (0.00 ± 0.54 kg; P = 0.99). In DSE, SAT and VAT did not change, but IMAT increased by 0.46 ± 0.55 kg (P < 0.001). Controlling for weight loss, reduction of specific AT depots was associated with improvement in metabolic biomarkers., Conclusions: Weight loss of 7-10% from an ILI over 1 year reduced SAT and VAT and prevented an increase in IMAT. Reductions in AT depots were associated with improvements in biomarkers., (© 2014 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.)

Whether lean body mass (LBM) composition, especially skeletal muscle and abdominal organs, differs in adults with type 2 diabetes (T2DM) compared with nondiabetic healthy controls has not been investigated. A subset of African-American and Caucasian participants with T2DM from the Look AHEAD (Action for Health in Diabetes) trial had body composition assessed and compared with a sample of healthy controls. Skeletal muscle mass (SMM), liver, kidneys, and spleen mass were quantified using a contiguous slice magnetic resonance imaging (MRI) protocol. Cardiac mass was quantified by either a cardiac gated MRI protocol or by echocardiography. MRI volumes were converted to mass using assumed densities. Dual-energy X-ray absorptiometry assessed LBM. Using general linear models adjusted for height, weight, sex, age, race, and interactions of diabetes status with race or sex, persons with T2DM (n = 95) had less LBM (49.7 vs. 51.6 kg) and SMM (24.1 vs. 25.4 kg) and larger kidneys (0.40 vs. 0.36 kg) than controls (n = 76) (all P < 0.01). Caucasians with T2DM had larger livers (1.90 vs. 1.60 kg, P < 0.0001) and spleens (0.29 vs. 0.22 kg, P < 0.01), and T2DM men had less cardiac mass than controls (0.25 vs. 0.30 kg, P < 0.001). In this sample, T2DM is characterized by less relative skeletal muscle and cardiac mass in conjunction with larger kidneys, liver, and spleen. Further investigation is needed to establish the causes and metabolic consequences of these race- and sex-specific organ mass differences in T2DM., (Copyright © 2014 the American Physiological Society.)

Dynamic positron emission tomography (PET) imaging was performed using sequential tracer injections ([(15)O]H2O, [(11)C]3-O-methylglucose [3-OMG], and [(18)F]fluorodeoxyglucose [FDG]) to quantify, respectively, skeletal muscle tissue perfusion (glucose delivery), kinetics of bidirectional glucose transport, and glucose phosphorylation to interrogate the individual contribution and interaction among these steps in muscle insulin resistance (IR) in type 2 diabetes (T2D). PET imaging was performed in normal weight nondiabetic subjects (NW) (n = 5), obese nondiabetic subjects (OB) (n = 6), and obese subjects with T2D (n = 7) during fasting conditions and separately during a 6-h euglycemic insulin infusion at 40 mU · m(-2) · min(-1). Tissue tracer activities were derived specifically within the soleus muscle with PET images and magnetic resonance imaging. During fasting, NW, OB, and T2D subjects had similar [(11)C]3-OMG and [(18)F]FDG uptake despite group differences for tissue perfusion. During insulin-stimulated conditions, IR was clearly evident in T2D (P < 0.01), and [(18)F]FDG uptake by muscle was inversely correlated with systemic IR (P < 0.001). The increase in insulin-stimulated glucose transport was less (P < 0.01) in T2D (twofold) than in NW (sevenfold) or OB (sixfold) subjects. The fractional phosphorylation of [(18)F]FDG during insulin infusion was also significantly lower in T2D (P < 0.01). Dynamic triple-tracer PET imaging indicates that skeletal muscle IR in T2D involves a severe impairment of glucose transport and additional impairment in the efficiency of glucose phosphorylation.

Objective: Objective measurements of physical activity (PA), energy expenditure (EE) and energy intake can provide valuable information regarding appropriate strategies for successful sustained weight loss., Design and Methods: The total EE was examined by doubly labeled water, resting metabolic rate by indirect calorimetry, PA with activity monitors, and energy intake by the intake/balance technique in 116 severely obese undergoing intervention with diet alone (DO) or diet plus PA (D-PA)., Results: Weight loss of 9.6 ± 6.8 kg resulted in decreased EE which was not minimized in the D-PA group. Comparing the highest and lowest quartiles of increase in PA revealed a lower decrease in TDEE (-122 ± 319 vs. -376 ± 305 kcal day⁻¹), elimination of the drop in AEE (83 ± 279 vs. -211 ± 284 kcal day⁻¹) and greater weight loss (13.0 ± 7.0 vs. 8.1 ± 6.3 kg). Increased PA was associated with greater adherence to energy restriction and maintenance of greater weight loss during months 7-12., Conclusion: Noncompliance to prescribed PA in the DO and D-PA groups partially masked the effects of PA to increase weight loss and to minimize the reduced EE. Increased PA was also associated with improved adherence to prescribed caloric restriction. A strong recommendation needs to be made to improve interventions that promote PA within the context of behavioral weight loss interventions., (Copyright © 2013 The Obesity Society.)

Purpose: Skeletal muscle insulin resistance (IR) often precedes hyperglycemia and type 2 diabetes. However, variability exists within different skeletal muscle types and can be influenced by 3 primary steps of control: glucose delivery, transport, and phosphorylation. We performed dynamic positron emission tomography imaging studies to determine the extent to which heterogeneity in muscle type and control of insulin action contribute to IR., Methods: Thirteen volunteers from normal weight to obese underwent dynamic positron emission tomography imaging of [15O]H2O, [11C]3-O-methylglucose, and [18F]fluorodeoxyglucose, measuring delivery, transport, and phosphorylation rates, respectively, in soleus and tibialis anterior muscle during a hyperinsulinemic-euglycemic clamp. Subjects were classified as insulin-sensitive (IS) or insulin-resistant (IR) based on the median systemic glucose infusion rate needed to maintain euglycemia., Results: In soleus, transport kinetic rates were significantly higher (P<.05) in IS (0.126±0.028 min(-1)) vs IR (0.051±0.008 min(-1)) subjects. These differences were not as evident in tibialis anterior. These differences were paralleled in overall insulin-stimulated tissue activity, higher in IS (0.017±0.001 mL·cm3·min(-1)) vs IR (0.011±0.002 mL·cm3·min(-1)) in soleus (P<.05), without significant differences in tibialis anterior. No significant differences were observed for either muscle in delivery or phosphorylation. Both muscle types displayed a control shift from an even distribution among the steps in IS to transport exerting greater control of systemic insulin sensitivity in IR., Conclusion: Lower glucose transport rates are the major feature underlying IR preceding type 2 diabetes, although substantial heterogeneity in insulin action across muscle types highlight the complexity of skeletal muscle IR.

Objective: The overexpression of the adipose gene (adp/WDTC1) in mice inhibits lipid accumulation and improves the metabolic profile. Subcutaneous fat adp expression in humans and its relation to metabolic parameters was evaluated., Design and Methods: Abdominal subcutaneous fat adp expression, insulin sensitivity (clamp), and respiratory quotient (RQ; indirect calorimetry) were assessed in: 36 obese and 56 BMI-, race-, and sex-matched type 2 diabetic volunteers (Look AHEAD Adipose Ancillary Study); 37 nondiabetic Pima Indians including obese (n = 18) and nonobese (n = 19) subjects and; 62 nonobese nondiabetic subjects at the Pennington Center in the ADAPT study., Results: In the Look AHEAD Study, adp expression normalized for cyclophilin B was higher in males versus females (1.27 ± 0.06 vs. 1.11 ± 0.04; P < 0.01) but not after controlling for body fat. Adp expression was not influenced by the presence of diabetes but was related to body fat (r = -0.23; P = 0.03), insulin sensitivity (r = 0.23; P = 0.03) and fasting/insulin-stimulated RQ (r = 0.31 and 0.33; P < 0.01). In Pima Indians, adp expression was also higher in males versus females (1.00 ± 0.05 vs. 0.77 ± 0.05; P = 0.02) and higher in nonobese versus obese (1.02 ± 0.05 vs. 0.80 ± 0.06; P = 0.03). In the ADAPT study, there was no difference in adp expression between males and females., Conclusion: Consistent with animal studies, our results suggest that high adp expression in human adipose tissue is associated with lower adiposity and enhanced glucose utilization., (Copyright © 2013 The Obesity Society.)

Background: We recently reported that Japanese had higher liver fat at a lower level of BMI compared with non-Hispanic whites (NHW)., Objective: We hypothesize that ethnic difference in fat storage capacity contributes to this ethnic difference in liver fat., Design: To examine this, we assessed liver fat among 244 Japanese-American aged 40-49, using regional computed-tomography images, along with metabolic variables., Results: Despite the similar BMI between Japanese-Americans and NHW men, Japanese-Americans had more liver fat (liver to spleen attenuation ratio: 1.03 ± 0.22 for Japanese-Americans, and 1.07 ± 0.15 for NHW men; p < 0.05) and tended to have a greater disposition for fatty liver with an increase in BMI than NHW, indicating a clear difference between the two groups. In addition, liver fat is less in Japanese-Americans compared with Japanese men (1.03 ± 0.22 vs. 1.01 ± 0.16; p < 0.05), despite of a much higher BMI. These ethnic differences support the hypothesis that higher fat storage capacity indeed seems to be associated with less liver fat. In all the groups, liver fat content strongly correlated with triglycerides, homeostasis model assessment-insulin resistance, and C-reactive protein (CRP). Nevertheless, these metabolic variables were worse in Japanese-Americans, despite of less liver fat, compared with Japanese. Moreover, CRP levels were least among Japanese with highest liver fat, and highest among NHW men with least liver fat, despite of a strong positive association between CRP and fatty liver within each population., Conclusions: Fat content in the liver is intermediate for Japanese-Americans compared with Japanese and NHW men, which supports the hypothesis of less fat storage capacity among Japanese, closely linked to ethnic difference in predisposition to fatty liver., (© 2011 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.)

Excess amounts of abdominal subcutaneous (SAT) and visceral (VAT) adipose tissue (AT) are associated with insulin resistance, even in normal-weight subjects. In contrast, gluteal-femoral AT (GFAT) is hypothesized to offer protection against insulin resistance. Dynamic PET imaging studies were undertaken to examine the contributions of both metabolic activity and size (volume) of these depots in systemic glucose metabolism. Nonobese, healthy volunteers (n = 15) underwent dynamic PET imaging uptake of [¹⁸F]FDG at a steady-state (20 mU·m⁻²·min⁻¹) insulin infusion. PET images of tissue [¹⁸F]FDG activity were coregistered with MRI to derive K values for insulin-stimulated rates of fractional glucose uptake within tissue. Adipose tissue volume was calculated from DEXA and MRI. VAT had significantly higher rates of fractional glucose uptake per volume than SAT (P < 0.05) or GFAT (P < 0.01). K(GFAT) correlated positively (r = 0.67, P < 0.01) with systemic insulin sensitivity [glucose disappearance rate (R(d))] and negatively with insulin-suppressed FFA (r = -0.71, P < 0.01). SAT (r = -0.70, P < 0.01) and VAT mass (r = -0.55, P < 0.05) correlated negatively with R(d), but GFAT mass did not. We conclude that rates of fractional glucose uptake within GFAT and VAT are significantly and positively associated with systemic insulin sensitivity in nonobese subjects. Furthermore, whereas SAT and VAT amounts are confirmed to relate to systemic insulin resistance, GFAT amount is not associated with insulin resistance. These dynamic PET imaging studies indicate that both quantity and quality of specific AT depots have distinct roles in systemic insulin resistance and may help explain the metabolically obese but normal-weight phenotype.