Biased agonism of the glucagon-like peptide-1/glucose-dependent insulinotropic polypeptide receptors (GLP-1R/GIPR) yields greater weight loss and better glycemic control than unbiased agonism in preclinical models. To evaluate whether biased agonism translates into improved efficacy for weight loss and glycemic control in clinical settings, we developed and characterized CT-388, a unimolecular peptide-based dual GLP-1R/GIPR agonist that is cAMP signal-biased at both receptors. In cell-based assays, CT-388 activated GLP-1R and GIPR with both having minimal receptor internalization vs their native ligands. CT-388 improved glycemic control in mice and monkeys, and reduced bodyweight, suppressed appetite, and improved metabolic dysfunction-associated steatohepatitis pathology in mice. In a phase 1, double-blind, randomized, placebo-controlled clinical study (NCT04838405) of CT-388 (subcutaneously administered single doses [0.5-7.5 mg] or 4 once-weekly doses [5-12 mg]) in otherwise healthy participants with overweight or obesity, CT-388 was generally well tolerated with a safety profile consistent with other incretin-based therapies; most treatment-emergent adverse events were mild or moderate. Glycemic parameters were improved during fasting conditions and an oral glucose tolerance test. The mean percent change in bodyweight from baseline to day 29 was -4.7% to -8.0% across CT-388 doses vs -0.5% with placebo. CT-388 pharmacokinetics supported once-weekly dosing. In conclusion, CT-388 demonstrated strong translatability from preclinical to clinical studies with consistent pharmacokinetics and pharmacodynamics across multiple species. In clinical settings, 4 weeks of CT-388 treatment produced clinically meaningful weight loss and improved glycemic control with favorable tolerability. These findings warrant further clinical evaluation of CT-388 for treating obesity and type 2 diabetes.

In lactating mothers, the high calcium (Ca2+) demand for milk production triggers significant bone loss1. Although oestrogen normally counteracts excessive bone resorption by promoting bone formation, this sex steroid drops precipitously during this postpartum period. Here we report that brain-derived cellular communication network factor 3 (CCN3) secreted from KISS1 neurons of the arcuate nucleus (ARCKISS1) fills this void and functions as a potent osteoanabolic factor to build bone in lactating females. We began by showing that our previously reported female-specific, dense bone phenotype2 originates from a humoral factor that promotes bone mass and acts on skeletal stem cells to increase their frequency and osteochondrogenic potential. This circulatory factor was then identified as CCN3, a brain-derived hormone from ARCKISS1 neurons that is able to stimulate mouse and human skeletal stem cell activity, increase bone remodelling and accelerate fracture repair in young and old mice of both sexes. The role of CCN3 in normal female physiology was revealed after detecting a burst of CCN3 expression in ARCKISS1 neurons coincident with lactation. After reducing CCN3 in ARCKISS1 neurons, lactating mothers lost bone and failed to sustain their progeny when challenged with a low-calcium diet. Our findings establish CCN3 as a potentially new therapeutic osteoanabolic hormone for both sexes and define a new maternal brain hormone for ensuring species survival in mammals. A brain-derived hormone, CCN3, is newly identified to have a role as an osteoanabolic factor to build bone in lactating females and in the viability of offspring.

Metabolic Syndrome (MetS) affects more than 30% of the US population and unmanaged can lead to cardiovascular disease and type II diabetes mellitus. MetS is a cluster of conditions, which include elevated arterial pressure, poor glucose tolerance with or without insulin resistance, and abdominal obesity. Existing literature has demonstrated high cholesterol diet’s (HCD) potential to develop MetS cluster factor conditions like dyslipidemia. Our lab has previously shown that angiotensin receptor blockers (ARBs), a common therapy to treat hypertension by disrupting the renin-angiotensin-aldosterone system (RAAS), attenuate cluster factor conditions of MetS. However, the efficacy of ARBs during the consumption of a HCD remains unclear. Otsuka Long Evan Tokushima Fatty (OLETF) rats (a MetS model) were fed an HCD and at presentation of elevated arterial pressure, they were treated with ARB (10 mg olmesartan/kg/d x 3 wks) by oral gavage. Blood pressure was monitored in real-time with surgically implanted radio telemeters. ARB reduced systolic blood pressure by 15±1mmHg (11%; p<0.05). ARB also reduced BM by 3% (p<0.05) in chow-fed and 4% (p<0.05) in HCD-fed OLETF compared to OLETF. However, there was no difference in BM between OLETF+ARB and OLETF+HCD+ARB. Neither, HCD nor ARB alone reduced abdominal fat in OLETF rats. Although, ARB in OLETF+HCD induced visceral fat loss (37%; p<0.05) compared to OLETF. Additionally, ARB reduced AUCglucose by 28% (P<0.05) and tended to reduce fasting blood glucose by 19% (p=0.06). These findings demonstrate that chronic treatment of ARB can effectively ameliorate MetS-associated hypertension, hyperglycemia, and abdominal obesity despite the additional insult of a HCD. This work was supported by the National Institutes of Health NCMHD 9T37MD001480 and National Institutes of Health, National Center on Minority Health and Health Disparities. E.E.J was supported by NIH GRISE BIO-STeP. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Objective: Cardiovascular disease (CVD) is the leading cause of death in the US (1 in 4) and is a primary outcome of Metabolic Syndrome (MetS). MetS affects nearly 40% of adults over 60 and is defined by a cluster of conditions including elevated arterial pressure and excess abdominal fat. A high cholesterol diet (HCD) is known to promote cluster-factor conditions of MetS. Unfortunately, body mass (BM) reduction is often insufficient to reduce hypertension. The first line of pharmaceutical defense is disruption of the renin-angiotensin aldosterone system (RAS). Inappropriate elevation of RAS can be therapeutically attenuated with angiotensin receptor blocker (ARBs), which has been shown to ameliorate other MetS cluster factor conditions. However, the efficacy of ARB on elevated arterial pressure during a HCD remains unclear. Design: A cohort of 5-week-old Otsuka Long Evan Tokushima Fatty (OLETF) rats were fed a HCD (2% + 0.5% cholic acid) or chow ad libitium. After 4 weeks, animals were treated with ARB (10 mg olmesartan /kg/d x 3 wks by oral gavage) and assigned to five groups: 1) lean-strain control Long Tokushima Evans Otsuka (LETO; n = 10), 2) OLETF (OLETF; n = 12), 3) OLETF+HCD (n = 12), 4) OLETF+ARB (n = 12) and 5) OLETF+HCD+ARB (n = 12). Systolic blood pressure was monitored chronically by radio telemetery. Results: OLETF SBP was 31% (p < 0.05) greater than LETO. HCD did not exacerbate elevated SBP in OLETF. ARB reduced SBP in OLETF + HCD by 11% (p < 0.05) over 30 days and 13% (p < 0.05) overall compared to OLETF. ARB reduced BM by 3% (p < 0.05) in chow-fed and 4% (p < 0.05) in HCD-fed OLETF compared to OLETF. However, there was no difference in BM between OLETF+ARB and OLETF+HCD+ARB. Neither, HCD nor ARB alone reduced abdominal fat in OLETF rats. ARB in OLETF+HCD induced visceral fat loss (37%; p < 0.05) compared to OLETF. ARB administration did not attenuate plasma angiotensin II levels. Conclusion: These findings demonstrate that chronic treatment with ARB can effectively ameliorate the MetS-associated hypertension despite the additional insult of a HCD.

The comet assay in Drosophila has been used in the last few years to study DNA damage responses (DDR) in different repair-mutant strains and to compare them to analyze DNA repair. We have used this approach to study interactions between DNA repair pathways in vivo. Additionally, we have implemented an ex vivo comet assay, in which nucleoids from treated and untreated cells were incubated ex vivo with cell-free protein extracts from individuals with distinct repair capacities. Four strains were used: wild-type OregonK (OK), nucleotide excision repair mutant mus201, dmPolQ protein mutant mus308, and the double mutant mus201;mus308. Methyl methanesulfonate (MMS) was used as a genotoxic agent. Both approaches were performed with neuroblasts from third-instar larvae; they detected the effects of the NER and dmPolQ pathways on the DDR to MMS and that they act additively in this response. Additionally, the ex vivo approach quantified that mus201, mus308, and the double mutant mus201;mus308 strains presented, respectively, 21.5%, 52.9%, and 14.8% of OK strain activity over MMS-induced damage. Considering the homology between mammals and Drosophila in repair pathways, the detected additive effect might be extrapolated even to humans, demonstrating that Drosophila might be an excellent model to study interactions between repair pathways.

The onset of type II diabetes increases the heart’s susceptibility to oxidative damage because of the associated inflammation and diminished antioxidant response. Transcription factor NF-κB initiates inflammation while Nrf2 controls antioxidant defense. Current evidence suggests crosstalk between these transcription factors that may become dysregulated during type II diabetes mellitus (T2DM) manifestation. The objective of this study was to examine the dynamic changes that occur in both transcription factors and target genes during the progression of T2DM in the heart. Novel UC Davis T2DM (UCD-T2DM) rats at the following states were utilized: (1) lean, control Sprague-Dawley (SD; n = 7), (2) insulin-resistant pre-diabetic UCD-T2DM (Pre; n = 9), (3) 2-week recently diabetic UCD-T2DM (2Wk; n = 9), (4) 3-month diabetic UCD-T2DM (3Mo; n = 14), and (5) 6-month diabetic UCD-T2DM (6Mo; n = 9). NF-κB acetylation increased 2-fold in 3Mo and 6Mo diabetic animals compared to SD and Pre animals. Nox4 protein increased 4-fold by 6Mo compared to SD. Nrf2 translocation increased 82% in Pre compared to SD but fell 47% in 6Mo animals. GCLM protein fell 35% in 6Mo animals compared to Pre. Hmox1 mRNA decreased 45% in 6Mo animals compared to SD. These data suggest that during the progression of T2DM, NF-κB related genes increase while Nrf2 genes are suppressed or unchanged, perpetuating inflammation and a lesser ability to handle an oxidant burden altering the heart’s redox state. Collectively, these changes likely contribute to the diabetes-associated cardiovascular complications.

Metabolic syndrome (MetS) is a rapidly increasing health concern during midlife and is an emerging risk factor for the development of neurodegenerative diseases, such as Alzheimer's disease (AD). While angiotensin receptor blockers (ARB) are widely used for MetS‐associated hypertension and kidney disease, its therapeutic potential in the brain during MetS are not well‐described. Here, we tested whether treatment with ARB could alleviate the brain pathology and inflammation associated with MetS using the Otsuka Long–Evans Tokushima Fatty (OLETF) rat. Here, we report that chronic ARB treatment with olmesartan (10 mg/kg/day by oral gavage for 6 weeks) partially but significantly ameliorated accumulation of oxidized and ubiquitinated proteins, astrogliosis and transformation to neurotoxic astrocytes in the brain of old OLETF rats, which otherwise exhibit the progression of these pathological hallmarks associated with MetS. Additionally, olmesartan treatment restored claudin‐5 and ZO‐1, markers of the structural integrity of the blood–brain barrier as well as synaptic protein PSD‐95, which were otherwise decreased in old OLETF rats, particularly in the hippocampus, a critical region in cognition, memory and AD. These data demonstrate that the progression of MetS in OLETF rats is associated with deterioration of various aspects of neuronal integrity that may manifest neurodegenerative conditions and that overactivation of angiotensin receptor directly or indirectly contributes to these detriments. Thus, olmesartan treatment may slow or delay the onset of degenerative process in the brain and subsequent neurological disorders associated with MetS.

Non-alcoholic fatty liver disease (NAFLD) affects up to 20% of the world's population. Overactivation of the angiotensin receptor type 1 (AT1) contributes to metabolic dysfunction and increased oxidant production, which are associated with NAFLD and impaired hepatic lipid metabolism. Nuclear factor erythroid-2-related factor 2 (Nrf2) regulates the expression of antioxidant phase II genes by binding to the antioxidant response element (ARE); however, the mechanisms by which AT1 contributes to this pathway during the progression of NAFLD remain unresolved. To investigate hepatic Nrf2 response to a hyperglycemic challenge, we studied three groups of rats (male, 10-weeks-old): (1) untreated, lean Long Evans Tokushima Otsuka (LETO), (2) untreated, obese Otsuka Long Evans Tokushima Fatty (OLETF), and (3) OLETF + angiotensin receptor blocker (OLETF + ARB; 10 mg olmesartan/kg/d × 6 weeks). Livers were collected after overnight fasting (T0; baseline), and 1 h and 2 h post-oral glucose load. At baseline, chronic AT1 blockade increased nuclear Nrf2 content, reduced expression of glutamate-cysteine ligase catalytic (GCLC) subunit, glutathione peroxidase 1 (GPx1), and superoxide dismutase 2 (SOD2), mitochondrial catalase activity, and hepatic 4-hydroxy-2-nonenal (4-HNE) content. The expression of hepatic interleukin-1 beta (IL-1β) and collagen type IV, which are associated with liver fibrosis, were decreased with AT1 blockade. Glucose increased Nrf2 translocation in OLETF but was reduced in ARB, suggesting that glucose induces the need for antioxidant defense that is ameliorated with ARB. These results suggest that overactivation of AT1 promotes oxidant damage by suppressing Nrf2 and contributing to hepatic fibrosis associated with NAFLD development.

Increased angiotensin II (Ang II) signaling contributes to insulin resistance and liver steatosis. In addition to ameliorating hypertension, angiotensin receptor blockers (ARBs) improve lipid metabolism and hepatic steatosis, which are impaired with metabolic syndrome (MetS). Chronic blockade of the Ang II receptor type 1 (AT1) increases plasma angiotensin 1-7 (Ang 1-7), which mediates mechanisms counterregulatory to AT1 signaling. Elevated plasma Ang 1-7 is associated with decreased plasma triacylglycerol (TAG), cholesterol, glucose, and insulin; however, the benefits of RAS modulation to prevent non-alcoholic fatty liver disease (NAFLD) are not fully investigated. To better address the relationships among chronic ARB treatment, plasma Ang 1-7, and he-patic steatosis, three groups of 10-week-old-rats were studied: (1) untreated lean Long Evans Tokushima Otsuka (LETO), (2) untreated Otsuka Long Evans Tokushima Fatty (OLETF), and (3) OLETF + ARB (ARB; 10 mg olmesartan/kg/d x 6 weeks). Following overnight fasting, rats underwent an acute glucose load to better un-derstand the dynamic metabolic responses during hepatic steatosis and early MetS. Tissues were collected at baseline (pre-load; T0) and 1 and 2 h post-glucose load. AT1 blockade increased plasma Ang 1-7 and decreased liver lipids, which was associated with decreased fatty acid transporter 5 (FATP5) and fatty acid synthase (FASN) expression. AT1 blockade decreased liver glucose and increased glucokinase (GCK) expression. These results demonstrate that during MetS, overactivation of AT1 promotes hepatic lipid deposition that is stimulated by an acute glucose load and lipogenesis genes, suggesting that the chronic hyperglycemia associated with MetS contributes to fatty liver pathologies via an AT1-mediated mechanism.

Inappropriate activation of the renin-angiotensin system increases adipocyte inflammation contributing to the impairment in adipocyte function and increases hepatic PCK1 and G6PC1 mRNA expression in response to a glucose challenge. Ultimately, these effects may contribute to the development of glucose intolerance.

Abstract Loss of peripheral estrogen in postmenopausal women is often associated with decreased physical activity and loss of bone mass, leading to an increased risk of metabolic diseases, osteoporosis, and skeletal fragility. While it is well-established that loss of peripheral estrogen signaling results in bone loss, we previously found that eliminating central estrogen signaling paradoxically results in an unexpected massive increase in bone mass only in female mice. Specifically, deletion of estrogen receptor alpha (ERα) signaling in kisspeptin 1 (Kiss1) expressing neurons of the arcuate nucleus (ARCKiss1) increases bone mass at the expense of reproduction in female mice. Currently, the mechanisms and the neurocircuits that modulate these unexpected responses are unknown. Here, to begin addressing these questions, we asked if changing the neuronal output of ARCKiss1 neurons using chemogenetic manipulation of ARCKiss1 neurons might also alter bone mass and locomotion in female mice. To do this, we delivered stimulatory (AAV2-hM3Dq-mCherry) designer receptors exclusively activated by designer drugs (DREADDs) to the ARC of wild type and Kiss1-Cre+ (Kiss1-CrehM3q-DREADDs) female mice and asked if chronic activation of ARCKiss1 neurons might alter bone mass as analyzed by standard ex-vivo µCT imaging. Clozapine N-oxide (CNO) was delivered for 22 days (0.1 mg/mL). We also leveraged the ANY-Maze system to assess home cage activity over an extensive 96-hour period. Acute activation of ARCKiss1 tended to decrease home cage activity by nearly 40% in Kiss1-CrehM3q-DREADDs mice during the dark period compared to WT females. Interestingly, chronic activation of ARCKiss1 neurons significantly lowered trabecular bone volume by nearly 30%. Current studies are underway to ask if inhibiting ARCKiss1 neurons results in increased bone mass. Our findings collectively suggest that the neuronal activity of ARCKiss1 neurons is sufficient to shift energy allocation away from locomotion and bone-building to maximize reproductive capacity. We speculate that the widely used SERM in breast cancer treatment, Tamoxifen, might exert its bone sparing effect by silencing ARCKiss1 neurons.

Oestrogen depletion in rodents and humans leads to inactivity, fat accumulation and diabetes 1 , 2 , underscoring the conserved metabolic benefits of oestrogen that inevitably decrease with age. In rodents, the preovulatory surge in 17β-oestradiol (E2) temporarily increases energy expenditure to coordinate increased physical activity with peak sexual receptivity. Here we report that a subset of oestrogen-sensitive neurons in the ventrolateral ventromedial hypothalamic nucleus (VMHvl) 3 – 7 projects to arousal centres in the hippocampus and hindbrain, and enables oestrogen to rebalance energy allocation in female mice. Surges in E2 increase melanocortin-4 receptor (MC4R) signalling in these VMHvl neurons by directly recruiting oestrogen receptor-α (ERα) to the Mc4r gene. Sedentary behaviour and obesity in oestrogen-depleted female mice were reversed after chemogenetic stimulation of VMHvl neurons expressing both MC4R and ERα. Similarly, a long-term increase in physical activity is observed after CRISPR-mediated activation of this node. These data extend the effect of MC4R signalling — the most common cause of monogenic human obesity 8 — beyond the regulation of food intake and rationalize reported sex differences in melanocortin signalling, including greater disease severity of MC4R insufficiency in women 9 . This hormone-dependent node illuminates the power of oestrogen during the reproductive cycle in motivating behaviour and maintaining an active lifestyle in women.

Estrogen depletion in rodents and humans leads to inactivity, unhealthy fat accumulation, and diabetes 1,2 , underscoring the conserved metabolic benefits of estrogen that inevitably decline with aging. In rodents, the preovulatory surge in 17β-estradiol (E2) temporarily allows energy expenditure to outpace energy intake, thus coordinating increased physical activity with peak sexual receptivity. To investigate how estrogen rebalances energy allocation in females, we examine estrogen receptor alpha (ERα) signaling in the ventrolateral ventromedial hypothalamic nucleus (VMHvl) 3–7 . We uncover a small population of VMHvl ERα neurons expressing the melanocortin-4 receptor (MC4R) that integrates estrogen and melanocortin signals and projects to arousal centers in the hippocampus and hindbrain, enabling bursts of physical activity. ERα recruitment to the Mc4r gene promotes upregulation of Mc4r in VMHvl neurons during the preovulatory surge or following E2 treatment. We leveraged three models to stimulate VMHvl MC4R neurons, restore MC4R signaling in the VMHvl of hyperphagic MC4R null females, or increase Mc4r levels in the VMHvl by CRISPR-mediated activation. All models increase spontaneous activity, whereas silencing VMHvl MC4R neurons blunts normal activity. Direct activation of the VMHvl MC4R node overrides the inactivity and hypometabolism following hormone depletion. These data extend the impact of MC4R signaling – the most common cause of monogenic human obesity 8 – beyond the regulation of food intake. Our findings also rationalize reported sex differences in melanocortin signaling, including the greater disease severity of MC4R insufficiency in women 9 . The hormone-dependent node identified here illuminates the power of estrogen in motivating behavior during the female reproductive cycle and for maintaining an active lifestyle.

Insulin resistance increases renal oxidant production by upregulating NADPH oxidase 4 (Nox4) expression contributing to oxidative damage and ultimately albuminuria. Inhibition of the renin‐angiotensin system (RAS) and activation of glucagon‐like peptide‐1 (GLP‐1) receptor signalling may reverse this effect. However, whether angiotensin receptor type 1 (AT1) blockade and GLP‐1 receptor activation improve oxidative damage and albuminuria through different mechanisms is not known. Using insulin‐resistant Otsuka Long‐Evans Tokushima Fatty (OLETF) rats, we tested the hypothesis that simultaneous blockade of AT1 and activation of GLP‐1r additively decrease oxidative damage and urinary albumin excretion (U alb V) in the following groups: (a) untreated, lean LETO (n = 7), (b) untreated, obese OLETF (n = 9), (c) OLETF + angiotensin receptor blocker (ARB; 10 mg olmesartan/kg/d; n = 9), (d) OLETF + GLP‐1 mimetic (EXE; 10 µg exenatide/kg/d; n = 7) and (e) OLETF + ARB +exenatide (Combo; n = 6). Mean kidney Nox4 protein expression and nitrotyrosine (NT) levels were 30% and 46% greater, respectively, in OLETF compared with LETO. Conversely, Nox4 protein expression and NT were reduced to LETO levels in ARB and EXE, and Combo reduced Nox4, NT and 4‐hydroxy‐2‐nonenal levels by 21%, 27% and 27%, respectively. At baseline, U alb V was nearly double in OLETF compared with LETO and increased to nearly 10‐fold greater levels by the end of the study. Whereas ARB (45%) and EXE (55%) individually reduced U alb V, the combination completely ameliorated the albuminuria. Collectively, these data suggest that AT1 blockade and GLP‐1 receptor activation reduce renal oxidative damage similarly during insulin resistance, whereas targeting both signalling pathways provides added benefit in restoring and/or further ameliorating albuminuria in a model of diet‐induced obesity.

Hyperglycemia increases the risk of oxidant overproduction in the heart through activation of a multitude of pathways. Oxidation of mitochondrial enzymes may impair their function resulting in accumulation of intermediates and reverse electron transfer, contributing to mitochondrial dysfunction. Furthermore, the renin‐angiotensin system (RAS) becomes inappropriately activated during metabolic syndrome, increasing oxidant production through NAPDH assemblage. To test the acute effects of an oral glucose tolerance test (oGTT) on the insulin resistant and type II diabetic hearts, 16 and 25 week old animals were given a glucose tolerance test prior to dissection. Adult male rats were randomly assigned to three groups prior to dissection (n= 5–8 animals/group/time point): 1) Long Evans Tokushima Otsuka (LETO; lean strain‐control), 2) insulin resistant, obese Otsuka Long Evans Tokushima Fatty (OLETF), and 3) OLETF + angiotensin receptor blocker (ARB; 10 mg olmesartan/kg/d x 6–8 weeks). Hearts were collected at T0, T60, and T120 minutes post‐glucose infusion and at T0, T180, and T360 in 25‐week‐old animals. Aconitase activity was not changed between LETO and OLETF rats at T0, but was increased five‐fold with ARB treatment. At T60 aconitase activity was decreased 69% in OLETF from LETO, but ARB treatment increased activity six‐fold. AT 25 weeks of age aconitase activity was two‐fold higher in OLETF compared to LETO and remained unchanged through T360. ARB treatment lowered this activity to LETO levels at T0 only. Complex I activity had no detectable difference between LETO and OLETF in 16 week old animals; however, ARB increased activity by 50%. However, in 25 week old animals complex I was lowered 32% from LETO and ARB treatment had no effect on complex I activity. At T60, complex II activity was decreased 30% from LETO in OLETF rats, and ARB treatment increased complex II activity by 79%. In 25 week old animals OLETF rats had increased complex II activity at T180 by 34%, which then was restored to baseline by T360. ARB treatment increased activity by 26%, but maintained this increase over the 6 hour span. These data demonstrate the protective effects of AT1 blockade on cardiac mitochondrial function during the manifestation of insulin resistance, but demonstrate that its protective effects diminish as animals transition into a frank diabetic stage.Support or Funding InformationM. Thorwald and R. Rodriguez were supported by NIH NCMHD9T37MD001480. R.M. Ortiz was partially supported by NIH NHLBIK02HL103787. Research was partially funded by NIH NHLBIR01HL091767.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Pathological activation of the renin-angiotensin system and inflammation are associated with hypertension and the development of metabolic syndrome (MetS). The contributions of angiotensin receptor type 1 (AT1) activation, independent of blood pressure, and inflammation to glucose intolerance and renal damage are not well defined. Using a rat model of MetS, we hypothesized that the onset of glucose intolerance is primarily mediated by AT1 activation and inflammation independent of elevated systolic blood pressure (SBP). To address this hypothesis, we measured changes in SBP, adiposity, plasma glucose and triglyceride levels, and glucose tolerance in six groups of rats: 1) lean, strain control Long-Evans Tokushima Otsuka (LETO; n = 5), 2) obese Otsuka Long-Evans Tokushima Fatty (OLETF; n = 8), 3) OLETF + angiotensin receptor blocker (ARB; 10 mg olmesartan/kg; n = 8), 4) OLETF + tumor necrosis factor-α (TNF-α) inhibitor (ETAN; 1.25 mg etanercept/kg; n = 6), 5) OLETF + TNF-α inhibitor + angiotensin receptor blocker (ETAN+ARB; 1.25 mg etanercept/kg + 10 mg olmesartan/kg; n = 6), and 6) OLETF + calcium channel blocker (CCB; 5 mg amlodipine/kg; n = 7). ARB and ETAN+ARB were most effective at decreasing SBP in OLETF, and ETAN did not offer any additional reduction. Glucose tolerance improved in ARB, ETAN, and ETAN+ARB compared with OLETF, whereas CCB had no detectable effect. Furthermore, all treatments reduced adiposity, whereas ETAN alone normalized urinary albumin excretion. These results suggest that AT1 activation and inflammation are primary factors in the development of glucose intolerance in a setting of MetS and that the associated increase in SBP is primarily mediated by AT1 activation.

Obesity is associated with an inappropriately activated renin–angiotensin–aldosterone system, suppressed glucagon-like peptide-1 (GLP-1), increased renal Na+ reabsorption, and hypertension. To assess the link between GLP-1 and angiotensin receptor type 1 (AT1) signaling on obesity-associated impairment of urinary Na+ excretion (UNaV) and elevated arterial pressure, we measured mean arterial pressure (MAP) and heart rate by radiotelemetry and metabolic parameters for 40 days. We tested the hypothesis that stimulation of GLP-1 signaling provides added benefit to blockade of AT1 by increasing UNaV and further reducing arterial pressure in the following groups: (1) untreated Long–Evans Tokushima Otsuka (LETO) rats (n = 7); (2) untreated Otsuka Long–Evans Tokushima Fatty (OLETF) rats (n = 9); (3) OLETF + ARB (ARB; 10 mg olmesartan/kg/day; n = 9); (4) OLETF + GLP-1 receptor agonist (EXE; 10 µg exenatide/kg/day; n = 7); and (5) OLETF + ARB + EXE (Combo; n = 6). On day 2, UNaV was 60% and 62% reduced in the EXE and Combo groups, respectively, compared with that in the OLETF rats. On day 40, UNaV was increased 69% in the Combo group compared with that in the OLETF group. On day 40, urinary angiotensinogen was 4.5-fold greater in the OLETF than in the LETO group and was 56%, 62%, and 58% lower in the ARB, EXE, and Combo groups, respectively, than in the OLETF group. From day 2 to the end of the study, MAP was lower in the ARB and Combo groups than in the OLETF rats. These results suggest that GLP-1 receptor activation may reduce intrarenal angiotensin II activity, and that simultaneous blockade of AT1 increases UNaV in obesity; however, these beneficial effects do not translate to a further reduction in MAP.

Obesity is associated with the inappropriate activation of the renin-angiotensin system (RAS), which increases arterial pressure, impairs insulin secretion and decreases peripheral tissue insulin sensitivity. RAS blockade reverses these detriments; however, it is not clear whether the disease state of the organism and treatment duration determine the beneficial effects of RAS inhibition on insulin secretion and insulin sensitivity. Therefore, the objective of this study was to compare the benefits of acute vs chronic angiotensin receptor type 1 (AT 1 ) blockade started after the onset of obesity, hyperglycemia and hypertension on pancreatic function and peripheral insulin resistance. We assessed adipocyte morphology, glucose intolerance, pancreatic redox balance and insulin secretion after 2 and 11 weeks of AT 1 blockade in the following groups of rats: (1) untreated Long-Evans Tokushima Otsuka (lean control; n = 10), (2) untreated Otsuka Long-Evans Tokushima Fatty (OLETF; n = 12) and (3) OLETF + ARB (ARB; 10 mg olmesartan/kg/day by oral gavage; n = 12). Regardless of treatment duration, AT 1 blockade decreased systolic blood pressure and fasting plasma triglycerides, whereas chronic AT 1 blockade decreased fasting plasma glucose, glucose intolerance and the relative abundance of large adipocytes by 22, 36 and 70%, respectively. AT 1 blockade, however, did not improve pancreatic oxidative stress or reverse impaired insulin secretion. Collectively, these data show that AT 1 blockade after the onset of obesity, hyperglycemia and hypertension improves peripheral tissue insulin sensitivity, but cannot completely reverse the metabolic derangement characterized by impaired insulin secretion once it has been compromised.

Hyperglycemia increases the risk of oxidant overproduction in the heart through activation of a multitude of pathways. Oxidation of mitochondrial enzymes may impair their function resulting in accumulation of intermediates and reverse electron transfer, contributing to mitochondrial dysfunction. Furthermore, the renin-angiotensin system (RAS) becomes inappropriately activated during metabolic syndrome, increasing oxidant production. To combat excess oxidant production, the transcription factor, nuclear factor erythriod-2- related factor 2 (Nrf2), induces expression of many antioxidant genes. We hypothesized that angiotensin II receptor type 1 (AT1) blockade improves mitochondrial function in response to an acute glucose load via upregulation of Nrf2. To address this hypothesis, an oral glucose challenge was performed in three groups prior to dissection (n = 5-8 animals/group/time point) of adult male rats: 1) Long Evans Tokushima Otsuka (LETO; lean strain-control), 2) insulin resistant, obese Otsuka Long Evans Tokushima Fatty (OLETF), and 3) OLETF + angiotensin receptor blocker (ARB; 10mg olmesartan/kg/d × 6 weeks). Hearts were collected at T0, T60, and T120 minutes post-glucose infusion. ARB increased Nrf2 binding 32% compared to OLETF at T60. Total superoxide dismutase (SOD) and catalase (CAT) activities were increased 45% and 66% respectively in ARB treated animals compared to OLETF. Mitochondrial enzyme activities of aconitase, complex I, and complex II increased by 135%, 33% and 66%, respectively in ARB compared to OLETF. These data demonstrate the protective effects of AT1 blockade on mitochondrial function during the manifestation of insulin resistance suggesting that the inappropriate activation of AT1 during insulin resistance may impair Nrf2 translocation and subsequent antioxidant activities and mitochondrial function.