Lysosomal glucose sensing and glycophagy in metabolism.

Lysosomes are cellular organelles that function to catabolize both extra- and intracellular cargo, act as a platform for nutrient sensing, and represent a core signaling node integrating bioenergetic cues to changes in cellular metabolism. Although lysosomal amino acid and lipid sensing in metabolism has been well characterized, lysosomal glucose sensing and the role of lysosomes in glucose metabolism is unrefined. This review will highlight the role of the lysosome in glucose metabolism with a focus on lysosomal glucose and glycogen sensing, glycophagy, and lysosomal glucose transport and how these processes impact autophagy and energy metabolism. Additionally, the role of lysosomal glucose metabolism in genetic and metabolic diseases will be briefly discussed.

ACOT1 deficiency attenuates high-fat diet-induced fat mass gain by increasing energy expenditure.

Acyl-CoA thioesterase 1 (ACOT1) catalyzes the hydrolysis of long-chain acyl-CoAs to free fatty acids and CoA and is typically upregulated in obesity. Whether targeting ACOT1 in the setting of high-fat diet-induced (HFD-induced) obesity would be metabolically beneficial is not known. Here we report that male and female ACOT1KO mice are partially protected from HFD-induced obesity, an effect associated with increased energy expenditure without alterations in physical activity or food intake. In males, ACOT1 deficiency increased mitochondrial uncoupling protein-2 (UCP2) protein abundance while reducing 4-hydroxynonenal, a marker of oxidative stress, in white adipose tissue and liver of HFD-fed mice. Moreover, concurrent knockdown (KD) of UCP2 with ACOT1 in hepatocytes prevented increases in oxygen consumption observed with ACOT1 KD during high lipid loading, suggesting that UCP2-induced uncoupling may increase energy expenditure to attenuate weight gain. Together, these data indicate that targeting ACOT1 may be effective for obesity prevention during caloric excess by increasing energy expenditure.

Organelle interactions compartmentalize hepatic fatty acid trafficking and metabolism.

Organelle interactions play a significant role in compartmentalizing metabolism and signaling. Lipid droplets (LDs) interact with numerous organelles, including mitochondria, which is largely assumed to facilitate lipid transfer and catabolism. However, quantitative proteomics of hepatic peridroplet mitochondria (PDM) and cytosolic mitochondria (CM) reveals that CM are enriched in proteins comprising various oxidative metabolism pathways, whereas PDM are enriched in proteins involved in lipid anabolism. Isotope tracing and super-resolution imaging confirms that fatty acids (FAs) are selectively trafficked to and oxidized in CM during fasting. In contrast, PDM facilitate FA esterification and LD expansion in nutrient-replete medium. Additionally, mitochondrion-associated membranes (MAM) around PDM and CM differ in their proteomes and ability to support distinct lipid metabolic pathways. We conclude that CM and CM-MAM support lipid catabolic pathways, whereas PDM and PDM-MAM allow hepatocytes to efficiently store excess lipids in LDs to prevent lipotoxicity.

Systemic lipolysis promotes physiological fitness in Drosophila melanogaster.

Since interventions such as caloric restriction or fasting robustly promote lipid catabolism and improve aging-related phenotypical markers, we investigated the direct effect of increased lipid catabolism via overexpression of bmm (brummer, FBgn0036449), the major triglyceride hydrolase in Drosophila, on lifespan and physiological fitness. Comprehensive characterization was carried out using RNA-seq, lipidomics and metabolomics analysis. Global overexpression of bmm strongly promoted numerous markers of physiological fitness, including increased female fecundity, fertility maintenance, preserved locomotion activity, increased mitochondrial biogenesis and oxidative metabolism. Increased bmm robustly upregulated the heat shock protein 70 (Hsp70) family of proteins, which equipped the flies with higher resistance to heat, cold, and ER stress via improved proteostasis. Despite improved physiological fitness, bmm overexpression did not extend lifespan. Taken together, these data show that bmm overexpression has broad beneficial effects on physiological fitness, but these effects did not impact lifespan.

Isolated and combined impact of dietary olive oil and exercise on markers of health and energy metabolism in female mice.

An olive oil (OO) rich diet or high-intensity interval training (HIIT) independently improve markers of health and energy metabolism, but it is unknown if combining OO and HIIT synergize to improve these markers. This study characterized the isolated and combined impact of OO and HIIT on markers of health and energy metabolism in various tissues in C57BL/6J female mice. Nine-week-old mice were divided into four groups for a 12-week diet and/or exercise intervention including: (1) Control Diet without HIIT (CD), (2) Control Diet with HIIT (CD+HIIT), (3) OO diet (10% kcal from olive oil) without HIIT, and (4) OO diet with HIIT (OO+HIIT). Neither dietary OO or HIIT altered body weight, glucose tolerance, or serum lipids. HIIT, regardless of diet, increased aerobic capacity and HDL cholesterol levels. In liver and heart tissue, OO resulted in similar adaptations as HIIT including increased mitochondrial content and fatty acid oxidation but combining OO with HIIT did not augment these effects. In skeletal muscle, HIIT increased mitochondrial content in type II fibers similarly between diets. An RNA sequencing analysis on type I fibers revealed OO reduced muscle regeneration and lipid metabolism gene abundance, whereas HIIT increased the abundance of these genes, independent of diet. HIIT training, independent of diet, induced subcutaneous white adipose tissue (sWAT) hypertrophy, whereas OO induced gonadal white adipose tissue (gWAT) hypertrophy, an effect that was augmented with HIIT. These data highlight the pleiotropic effects of OO and HIIT, although their combination does not synergize to further improve most markers of health and energy metabolism.

Regulation and role of glycophagy in skeletal muscle energy metabolism.

Glycophagy is the autophagic degradation of glycogen via the lysosomal enzyme GAA/alpha-acid glucosidase. Glycophagy is considered a housekeeping process to degrade poorly branched glycogen particles, but the regulation and role of glycophagy in skeletal muscle metabolism remains enigmatic. Herein, prior muscle contraction promoted glycogen supercompensation 24 and 48 h post contraction, an effect associated with reduced glycophagy. Moreover, NOTCH or cAMP signaling promoted glycophagy, whereas acute glycophagy deficiency rewired cell metabolism by reducing glycolysis and enhancing AMPK and PPAR signaling and fatty acid and glutamine metabolism. These metabolic adaptations were associated with reduced inflammation and triglyceride content but enhanced phosphoinositide 3-kinase (PI3K)-AKT/protein kinase B signaling and insulin action, the latter of which was abolished by exogenous oxidative stress. Collectively, these data suggest glycophagy is dynamically regulated, while the function of glycophagy can be extended beyond a housekeeping process to having an additional role in regulating energy metabolism and insulin action.Abbreviations: AMPK, AMP-activated protein kinase; ASM, acid soluble metabolites; cAMP, cyclic adenosine monophosphate; EPS, electrical pulse stimulation; FCCP, carbonyl cyanide-p-trifluoromethoxyphenylhydrazone; GAA, glucosidase, alpha, acid; mTOR, mechanistic target of rapamycin kinase; NAD, nicotinamide adenine dinucleotide; PARP, poly (ADP-ribose) polymerase family; PI3K, phosphoinositide 3-kinase; PPAR, peroxisome proliferator activated receptor ; PYGM, muscle glycogen phosphorylase; STBD1, starch binding domain 1; TFEB, transcription factor EB.

Muscle Lipid Droplets: Cellular Signaling to Exercise Physiology and Beyond.

Conventionally viewed as energy storage depots, lipid droplets (LDs) play a central role in muscle lipid metabolism and intracellular signaling, as recognized by recent advances in our biological understanding. Specific subpopulations of muscle LDs, defined by location and associated proteins, are responsible for distinct biological functions. In this review, the traditional view of muscle LDs is examined, and the emerging role of LDs in intracellular signaling is highlighted. The effects of chronic and acute exercise on muscle LD metabolism and signaling is discussed. In conclusion, future directions for muscle LD research are identified. The primary focus will be on human studies, with inclusion of select animal/cellular/non-muscle studies as appropriate, to provide the underlying mechanisms driving the observed findings.

Estrogen receptor-α in female skeletal muscle is not required for regulation of muscle insulin sensitivity and mitochondrial regulation.

OBJECTIVE: Estrogen receptor-α (ERα) is a nuclear receptor family member thought to substantially contribute to the metabolic regulation of skeletal muscle. However, previous mouse models utilized to assess the necessity of ERα signaling in skeletal muscle were confounded by altered developmental programming and/or influenced by secondary effects, making it difficult to assign a causal role for ERα. The objective of this study was to determine the role of skeletal muscle ERα in regulating metabolism in the absence of confounding factors of development. METHODS: A novel mouse model was developed allowing for induced deletion of ERα in adult female skeletal muscle (ERαKOism). ERαshRNA was also used to knockdown ERα (ERαKD) in human myotubes cultured from primary human skeletal muscle cells isolated from muscle biopsies from healthy and obese insulin-resistant women. RESULTS: Twelve weeks of HFD exposure had no differential effects on body composition, VO2, VCO2, RER, energy expenditure, and activity counts across genotypes. Although ERαKOism mice exhibited greater glucose intolerance than wild-type (WT) mice after chronic HFD, ex vivo skeletal muscle glucose uptake was not impaired in the ERαKOism mice. Expression of pro-inflammatory genes was altered in the skeletal muscle of the ERαKOism, but the concentrations of these inflammatory markers in the systemic circulation were either lower or remained similar to the WT mice. Finally, skeletal muscle mitochondrial respiratory capacity, oxidative phosphorylation efficiency, and H2O2 emission potential was not affected in the ERαKOism mice. ERαKD in human skeletal muscle cells neither altered differentiation capacity nor caused severe deficits in mitochondrial respiratory capacity. CONCLUSIONS: Collectively, these results suggest that ERα function is superfluous in protecting against HFD-induced skeletal muscle metabolic derangements after postnatal development is complete.

Lipid Droplet-Derived Monounsaturated Fatty Acids Traffic via PLIN5 to Allosterically Activate SIRT1.

Lipid droplets (LDs) provide a reservoir for triacylglycerol storage and are a central hub for fatty acid trafficking and signaling in cells. Lipolysis promotes mitochondrial biogenesis and oxidative metabolism via a SIRT1/PGC-1α/PPARα-dependent pathway through an unknown mechanism. Herein, we identify that monounsaturated fatty acids (MUFAs) allosterically activate SIRT1 toward select peptide-substrates such as PGC-1α. MUFAs enhance PGC-1α/PPARα signaling and promote oxidative metabolism in cells and animal models in a SIRT1-dependent manner. Moreover, we characterize the LD protein perilipin 5 (PLIN5), which is known to enhance mitochondrial biogenesis and function, to be a fatty-acid-binding protein that preferentially binds LD-derived monounsaturated fatty acids and traffics them to the nucleus following cAMP/PKA-mediated lipolytic stimulation. Thus, these studies identify the first-known endogenous allosteric modulators of SIRT1 and characterize a LD-nuclear signaling axis that underlies the known metabolic benefits of MUFAs and PLIN5.

Mitochondrial PE potentiates respiratory enzymes to amplify skeletal muscle aerobic capacity.

Exercise capacity is a strong predictor of all-cause mortality. Skeletal muscle mitochondrial respiratory capacity, its biggest contributor, adapts robustly to changes in energy demands induced by contractile activity. While transcriptional regulation of mitochondrial enzymes has been extensively studied, there is limited information on how mitochondrial membrane lipids are regulated. Here, we show that exercise training or muscle disuse alters mitochondrial membrane phospholipids including phosphatidylethanolamine (PE). Addition of PE promoted, whereas removal of PE diminished, mitochondrial respiratory capacity. Unexpectedly, skeletal muscle-specific inhibition of mitochondria-autonomous synthesis of PE caused respiratory failure because of metabolic insults in the diaphragm muscle. While mitochondrial PE deficiency coincided with increased oxidative stress, neutralization of the latter did not rescue lethality. These findings highlight the previously underappreciated role of mitochondrial membrane phospholipids in dynamically controlling skeletal muscle energetics and function.

Syncing Exercise With Meals and Circadian Clocks.

Circadian rhythms, meals, and exercise modulate energy metabolism. This review explores the novel hypothesis that there is an optimal time of day to exercise to improve 24 h glycemia and lipemia in individuals with type 2 diabetes.

A comparison of adipose tissue interstitial glucose and venous blood glucose during postprandial resistance exercise in patients with type 2 diabetes.

Resistance exercise during the postprandial period lowers venous glucose concentrations in individuals with type 2 diabetes, but the impact of resistance exercise on interstitial glucose concentrations is not well understood. The objective of this study was to compare subcutaneous adipose tissue interstitial glucose and venous blood glucose concentrations during postprandial resistance exercise in patients with type 2 diabetes. Eleven individuals completed two trials in a random order including a no-exercise (NoEx) and a postprandial resistance exercise trial (M-Ex). During the trials, the individuals consumed a meal and either remained sedentary (NoEx) or performed a session of resistance training beginning 45 min after the meal (M-Ex) while interstitial and venous glucose concentrations were simultaneously measured. Venous glucose during exercise was ~11% lower ( P = 0.05) during M-Ex (8.0 ± 0.5 mmol/l) compared with NoEx (9.0 ± 0.5 mmol/l) whereas interstitial glucose during M-Ex (10.4 ± 0.7 mmol/l) was not different compared with interstitial glucose during NoEx (10.1 ± 0.7 mmol/l). Bland-Altman plots revealed that the difference (bias) between interstitial and venous glucose during exercise was more than twofold greater during M-Ex (2.36 ± 2.07 mmol/l) compared with NoEx (1.11 ± 1.69 mmol/l). The mean (33.8 ± 6.2 mmol/l) and median (34.7 ± 6.3 mmol/l) absolute relative difference during exercise were 73% and 78% greater compared with the mean (19.5 ± 4.1 mmol/l) and median (19.5 ± 4.1 mmol/l) absolute relative difference during NoEx ( P = 0.04). Resistance exercise has unequal effects on glucose concentrations within different bodily compartments as exercise reduced venous glucose concentrations but not adipose tissue interstitial glucose concentrations in the abdominal region in individuals with type 2 diabetes. NEW & NOTEWORTHY This is the first study to compare subcutaneous adipose tissue interstitial glucose concentrations and venous blood glucose concentrations during postprandial resistance exercise in individuals with type 2 diabetes. We find that resistance exercise effectively reduces systemic venous blood glucose concentrations but not subcutaneous adipose tissue interstitial glucose concentrations in the abdominal region. Resistance exercise has differential effects on glucose concentrations depending on its compartmentalization within the body.

Greater Oxidative Capacity in Primary Myotubes from Endurance-trained Women.

PURPOSE: Exercise training promotes skeletal muscle mitochondrial biogenesis and an increase in maximal oxygen consumption. Primary myotubes retain some metabolic properties observed in vivo but it is unknown whether this includes exercise-induced mitochondrial adaptations. The goal of this study was to test if primary myotubes from exercise-trained women have higher mitochondrial content and maximal oxygen consumption compared with untrained women. METHODS: Six trained and nine untrained white women participated in this study. Muscle biopsies from the vastus lateralis muscle of the right leg were obtained and primary muscle cells were isolated. Maximal respiration rates, mitochondrial mRNA and protein content, and succinate dehydrogenase activity were measured in skeletal muscle and primary myotubes from trained and untrained women. RESULTS: Trained women, compared with untrained women, had higher maximal whole-body oxygen consumption (+18%, P = 0.03), in vivo maximal skeletal muscle oxidative capacity measured with near infrared spectroscopy (+48%, P < 0.01), and maximal oxygen consumption in permeabilized muscle fibers (+38%, P = 0.02), which coincided with higher protein levels of muscle mitochondrial enzymes. Primary myotubes from trained women had higher maximal oxygen consumption (+38%, P = 0.03), suggesting that some elements of exercise-induced metabolic programming persists ex vivo. Consistent with this idea, myotubes from trained women had higher mRNA levels of transcriptional regulators of mitochondrial biogenesis in addition to higher protein levels of mitochondrial enzymes. CONCLUSIONS: These data suggest the existence of an "exercise metabolic program," where primary myotubes isolated from exercise-trained individuals exhibit greater mitochondrial content and oxidative capacity compared with untrained individuals. These myotubes may be a useful model to study molecular mechanisms relevant to exercise adaptations in human skeletal muscle.

Exercise timing and blood lactate concentrations in individuals with type 2 diabetes.

The purpose of this study was to characterize how resistance exercise prior to or after a meal alters fasting and postprandial blood lactate concentrations in individuals with type 2 diabetes. Obese individuals with type 2 diabetes (N = 12) completed three 2-day trials, including (i) no exercise (NoEx), (ii) resistance exercise prior to dinner (Ex-M), and (iii) resistance exercise beginning at 45 min postdinner (M-Ex). During day 1 of each trial, fasting and postprandial blood lactate concentrations, perceived exertion, and substrate oxidation were measured, and subsequently on day 2 the following morning fasting blood lactate was measured. The premeal lactate incremental area under the curve (iAUC) during Ex-M (109 ± 66 mmol·L-1·1.6 h-1) was over 100-fold greater (P < 0.01) compared with NoEx (-15 ± 24 mmol·L-1·1.6 h-1) and M-Ex (-2 ± 18 mmol·L-1·1.6 h-1). The postprandial lactate iAUC during M-Ex (304 ± 116 mmol·L-1·4 h-1) was over 2-fold greater (P < 0.01) compared with NoEx (149 ± 74 mmol·L-1·4 h-1) and Ex-M (-140 ± 196 mmol·L-1·4 h-1). Average lactate during exercise was ∼45% greater (P = 0.03) during M-Ex (3.2 ± 0.9 mmol/L) compared with Ex-M (2.2 ± 0.9 mmol/L), but the change in lactate during Ex-M (2.4 ± 1.6 mmol/L) or M-Ex (2.3 ± 1.3 mmol/L) was not different (P > 0.05). Perceived exertion, substrate oxidation, or fasting blood lactate concentrations the day after testing were not different between trials. Blood lactate concentrations during acute resistance exercise are greater when exercise is performed in the postprandial period. Acute resistance exercise performed the night prior does not alter fasting blood lactate concentrations the following morning.

Plasma Irisin Modestly Increases during Moderate and High-Intensity Afternoon Exercise in Obese Females.

BACKGROUND AND PURPOSE: Irisin is an exercise-responsive myokine that has been proposed to exert anti-obesity benefits; yet its response during exercise in obese women is not described. This study characterized plasma irisin levels during a single bout of afternoon isocaloric-exercise of different intensities (moderate- vs high-intensity) in obese females. METHODS: Eleven obese females participated in 3 randomized study days beginning at 1600h: 1) no exercise (NoEx), 2) moderate exercise (ModEx; 55%VO2max) and 3) high intensity interval exercise (IntEx; 4 min (80%VO2max)/3 min (50% VO2max). Frequent blood samples were analyzed for glucose and lactate (whole-blood), and insulin, c-peptide, glucagon, and irisin (plasma) throughout 190 min of testing. RESULTS: Plasma irisin increased above baseline during ModEx and IntEx (P<0.05), but not NoEx (P>0.05). Peak irisin levels during ModEx and IntEx exercise were 11.9± 3.4% and 12.3 ± 4.1% relative to baseline (P<0.05), respectively, with no differences between exercise intensities (P>0.05). Irisin levels remained elevated above resting for 125 minutes post-exercise during ModEx, whereas levels returned to baseline within 15 minutes post-exercise during IntEx. Similarly, no associations were found between plasma irisin levels and circulating lactate, glucose, insulin, c-peptide, or glucagon among study days (P>0.05). However, there was an inverse association between basal irisin and lean mass (r = -0.70, P = 0.01). CONCLUSION: A single bout of moderate and high intensity afternoon exercise induces modest increases in circulating irisin concentrations during exercise; however the regulation post-exercise appears to be dimorphic between exercise intensity in obese females. Future studies are needed to compare morning and afternoon exercise on irisin secretion.

Looking Beyond Structure: Membrane Phospholipids of Skeletal Muscle Mitochondria.

Skeletal muscle mitochondria are highly dynamic and are capable of tremendous expansion to meet cellular energetic demands. Such proliferation in mitochondrial mass requires a synchronized supply of enzymes and structural phospholipids. While transcriptional regulation of mitochondrial enzymes has been extensively studied, there is limited information on how mitochondrial membrane lipids are generated in skeletal muscle. Herein we describe how each class of phospholipids that constitute mitochondrial membranes are synthesized and/or imported, and summarize genetic evidence indicating that membrane phospholipid composition represents a significant modulator of skeletal muscle mitochondrial respiratory function. We also discuss how skeletal muscle mitochondrial phospholipids may mediate the effect of diet and exercise on oxidative metabolism.

Impact of Exercise Timing on Appetite Regulation in Individuals with Type 2 Diabetes.

PURPOSE: Exercise improves appetite regulation, but it is not known if premeal or postmeal exercise more effectively improves appetite regulation in individuals with type 2 diabetes. For the first time, this study compared how premeal and postmeal exercise alters appetite regulation in individuals with type 2 diabetes. METHODS: Twelve obese individuals with type 2 diabetes performed 3 different trials, all in a random order, in which they consumed a dinner meal with the following: no resistance exercise (RE), premeal RE, or postmeal RE beginning 45 min after dinner. A visual analog scale was used to assess perceived hunger and fullness, and frequent blood samples were drawn for determination of acylated ghrelin, pancreatic polypeptide (PP), and peptide tyrosine tyrosine (PYY) concentrations. RESULTS: Premeal RE increased premeal perceived fullness, reduced perceived hunger, and reduced acylated ghrelin concentrations compared with the no RE and postmeal RE trial (P < 0.05). In the postprandial period, both premeal and postmeal RE reduced perceived hunger compared with no RE, whereas only postmeal RE reduced postprandial perceived fullness (P < 0.05) compared with no RE. Premeal or postmeal RE did not alter PYY concentrations. In both the premeal and postprandial period, RE reduced PP concentrations compared with no RE (P < 0.05), but upon cessation of RE, PP concentrations rebounded to concentrations that were similar to no RE. CONCLUSIONS: Both premeal and postmeal RE reduced perceived hunger and increased perceived fullness, effects that may help control food intake and aid in weight management efforts in individuals with type 2 diabetes.

High-Fat Diet Alters Serum Fatty Acid Profiles in Obesity Prone Rats: Implications for In Vitro Studies.

High-fat diets (HFD) are commonly used in rodents to induce obesity, increase serum fatty acids and induce lipotoxicity in various organs. In vitro studies commonly utilize individual free fatty acids (FFA) to study lipid exposure in an effort to model what is occurring in vivo; however, these approaches are not physiological as tissues are exposed to multiple fatty acids in vivo. Here we characterize circulating lipids in obesity-prone rats fed an HFD in both fasted and fed states with the goal of developing physiologically relevant fatty acid mixtures for subsequent in vitro studies. Rats were fed an HFD (60% kcal fat) or a control diet (10% kcal fat) for 3 weeks; liver tissue and both portal and systemic blood were collected. Fatty acid profiles and absolute concentrations of triglycerides (TAG) and FFA in the serum and TAG, diacylglycerol (DAG) and phospholipids in the liver were measured. Surprisingly, both systemic and portal serum TAG were ~40% lower in HFD-fed compared to controls. Overall, compared to the control diet, HFD feeding consistently induced an increase in the proportion of circulating polyunsaturated fatty acids (PUFA) with a concomitant decline in monounsaturated fatty acids (MUFA) and saturated fatty acids (SFA) in both serum TAG and FFA. The elevations of PUFA were mostly attributed to increases in n-6 PUFA, linoleic acid and arachidonic acid. In conclusion, fatty acid mixtures enriched with linoleic and arachidonic acid in addition to SFA and MUFA should be utilized for in vitro studies attempting to model lipid exposures that occur during in vivo HFD conditions.

Prior exercise does not alter the incretin response to a subsequent meal in obese women.

Prior research has shown an increase in GLP-1 concentrations during exercise but this exercise bout was conducted postprandially. The purpose of this study was to examine the incretin response to a meal following an exercise bout of different intensities in obese subjects. Eleven women (BMI>37.3±7.0kg/m(2); Age 24.3±4.6year) participated in 3 counter- balanced study days, where a standardized meal was preceded by: (1) No exercise (NoEx), (2) ModEx (55% VO2max), and (3) IntEx (4min (80% VO2max)/3min (50% VO2max). Frequent blood samples were analyzed for glucose, lactate, insulin, glucagon, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and C-peptide concentrations throughout 280min of testing. Glucose concentrations were not different between conditions during exercise or meals. There were no differences between conditions in insulin levels during exercise and recovery, but postprandial insulin incremental area under the curve was lower in ModEx vs. NoEx (p<0.01). GIP and GLP-1 levels were not different between conditions during exercise, but during exercise recovery, GLP-1 concentrations were higher in ModEx vs. NoEx (p=0.03). The meal increased the incretin responses (p<0.01) but this response was not affected by prior exercise. Glucagon concentrations increased with exercise (p<0.05) and continued to be elevated during recovery, with the greatest increase with IntEx compared with NoEx (p<0.05). No differences between conditions were detected for hepatic insulin extraction, insulin secretion, or insulin sensitivity. Exercise prior to an evening meal has no impact on the incretin response to the subsequent meal, yet insulin concentrations were lower during the meals that followed exercise. Exercise intensity had no impact on this response.