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Woolcott, Orison O., Till Seuring, and Oscar A. Castillo. Lower prevalence of body fat-defined obesity at higher altitudes in Peruvian adults. High Alt Med Biol . 24:214-222, 2023. Background: Previous studies have reported a lower prevalence of obesity (defined as a body mass index [BMI] ≥30 kg/m 2 ) in populations from higher altitudes. Since BMI does not distinguish fat mass and fat-free mass, it is unclear whether there is an inverse association between altitude and body fat-defined obesity. Methods: We performed an analysis of cross-sectional data to examine the association between altitude and body fat-defined obesity (as opposed to BMI-defined obesity) using individual-level data from a nationally representative sample of the Peruvian adult population living between 0 and 5,400 m altitude. Body fat-defined obesity was diagnosed using the relative fat mass (RFM), an anthropometric index validated to estimate whole-body fat percentage. RFM cutoffs for obesity diagnosis were ≥40% for women and ≥30% for men. We utilized Poisson regression to estimate the prevalence ratio and confidence intervals (CIs) as the measure of the association, adjusting for age, cigarette use, and diabetes. Results: Analysis comprised 36,727 individuals (median age, 39 years; 50.1% women). In rural areas, for a one-km increase in altitude, the prevalence of body fat-defined obesity decreased by 12% among women (adjusted prevalence ratio: 0.88; 95% CI, 0.86 - 0.90; p  < 0.001) and 19% among men (adjusted prevalence ratio: 0.81; 95% CI, 0.77 - 0.86; p  < 0.001), on average, when all the other variables were held constant. The inverse association between altitude and obesity was less strong in urban areas than in rural areas but remained significant among women ( p  = 0.001) and men ( p  < 0.001). However, the relationship between altitude and obesity in women who live in urban areas appears to be nonlinear. Conclusions: In Peruvian adults, the prevalence of body fat-defined obesity was inversely associated with altitude. Whether this inverse association is explained by altitude per se or confounded by socioeconomic or other environmental factors, or differences in race/ethnicity or lifestyle, warrants further investigation.

Objectives: The body mass index (BMI) largely underestimates excess body fat, suggesting that the prevalence of obesity could be underestimated. Biologically, women are known to have higher body fat than men. This study aimed to compare the temporal trends in general obesity by sex, ethnicity and age among adults in the USA using the relative fat mass (RFM), a validated surrogate for whole-body fat percentage and BMI., Design: Population-based study., Setting: US National Health and Nutrition Examination Survey, from 1999-2000 to 2017-March 2020., Participants: A representative sample of adults 20-79 years in the USA., Main Outcome Measures: Age-adjusted prevalence of general obesity. RFM-defined obesity was diagnosed using validated cut-offs to predict all-cause mortality: RFM≥40% for women and ≥30% for men. BMI-defined obesity was diagnosed using a cut-off of 30 kg/m 2 ., Results: Analysis included data from 47 667 adults. Among women, RFM-defined obesity prevalence was 64.7% (95% CI 62.1% to 67.3%) in 2017-2020, a linear increase of 13.9 percentage points (95% CI 9.0% to 18.9%; p<0.001) relative to 1999-2000. In contrast, the prevalence of BMI-defined obesity was 42.2% (95% CI 39.4% to 45.0%) in 2017-2020. Among men, the corresponding RFM-defined obesity prevalence was 45.8% (95% CI 42.0% to 49.7%), a linear increase of 12.0 percentage points (95% CI 6.6% to 17.3%; p<0.001). In contrast, the prevalence of BMI-defined obesity was 42.0 (95% CI 37.8% to 46.3%). The highest prevalence of RFM-defined obesity across years was observed in older adults (60-79 years) and Mexican Americans, in women and men. Conversely, the highest prevalence of BMI-defined obesity across years was observed in middle-age (40-59 years) and older adults, and in African American women., Conclusions: The use of a surrogate for whole-body fat percentage revealed a much higher prevalence of general obesity in the USA from 1999 to 2020, particularly among women, than that estimated using BMI, and detected a disproportionate higher prevalence of general obesity in older adults and Mexican Americans., Competing Interests: Competing interests: OOW is the lead author of the original article describing the development and validation of RFM. OOW currently works as an editor for The Lancet group., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: Sodium-glucose cotransporter 2 inhibitors (SGLT2i) promote urinary glucose excretion, induce weight loss, and reduce fat accumulation. The effects of the SGLT2i dapagliflozin (DAPA) on subcutaneous (SC) and visceral (VIS) adipose tissue function remain unclear. The objective of this study is to evaluate SC and VIS adipose tissue function in an insulin-resistant canine model., Methods: A total of 12 dogs were fed a high-fat diet (HFD) for 6 weeks and then were given a single low dose of streptozotocin (18.5 mg/kg) to induce insulin resistance. Animals were then randomized and exposed to DAPA (n = 6, 1.25 mg/kg) or placebo (n = 6) once per day for 6 weeks while remaining on the HFD., Results: DAPA prevented further weight gain induced by the HFD and normalized fat mass. DAPA reduced fasting glucose and increased free fatty acids, adiponectin, and β-hydroxybutyrate. DAPA reduced adipocyte diameter and cell distribution. Furthermore, DAPA increased genes associated with beiging, lipolysis, and adiponectin secretion and the expression of the adiponectin receptor ADR2, in SC and VIS adipose tissue. DAPA increased AMP-activated protein kinase activity and maximal mitochondrial respiratory function, especially in the SC depot. Furthermore, DAPA reduced cytokines and ceramide synthesis enzymes in SC and VIS depots., Conclusions: For the first time, to our knowledge, we identify mechanisms by which DAPA enhances adipose tissue function in regulating energy homeostasis in an insulin-resistant canine model., (© 2023 The Obesity Society.)

Diabetes is associated with severe COVID-19 and mortality. The aim of the present study was to determine the effect of age on the association between diabetes and mortality in patients with laboratory-confirmed COVID-19 in Mexico. This retrospective cohort study involved patients aged 20 years or older with symptoms of viral respiratory disease who were screened for SARS-CoV-2 infection across the System of Epidemiological Surveillance of Viral Respiratory Disease in Mexico from January 1 through November 4, 2020. Cox proportional-hazard regression was used to calculate the hazard ratio for 28-day mortality and its 95% confidence interval (CI). Among 757,210 patients with COVID-19 (outpatients and inpatients), 120,476 (16%) had diabetes and 80,616 died. Among 878,840 patients without COVID-19 (those who tested negative for SARS-CoV-2 infection), 88,235 (10.0%) had diabetes and 20,134 died. Among patients with COVID-19, diabetes was associated with a hazard ratio for death of 1.49 (95% CI 1.47-1.52), adjusting for age, sex, smoking habit, obesity, hypertension, immunodeficiency, and cardiovascular, pulmonary, and chronic renal disease. The strength of the association decreased with age (trend test: P = 0.004). For example, the adjusted hazard ratio for death was 3.12 (95% CI 2.86-3.40) for patients 20-39 years of age; in contrast, the adjusted hazard ratio of death for patients 80 years of age or older was 1.11 (95% CI 1.06-1.16). The adjusted hazard ratios were 1.66 (95% CI 1.58-1.74) in outpatients and 1.14 (95% CI 1.12-1.16) in inpatients. In hospitalized patients 80 years of age or older, no association was observed between diabetes and COVID-19-related mortality (adjusted hazard ratio: 1.03; 95% CI 0.98-1.08). Among patients without COVID-19, the adjusted hazard ratio for death was 1.78 (95% CI 1.73-1.84). In conclusion, in adult patients with COVID-19 in Mexico, the risk of death associated with diabetes decreased with age. No association between diabetes and mortality was observed among inpatients 80 years of age or older. Our findings should be verified in other populations.

Woolcott, Orison O., and Richard N. Bergman. Mortality attributed to COVID-19 in high-altitude populations. High Alt Med Biol . 21:409-416, 2020. Background: Since partial oxygen pressure decreases as altitude increases, environmental hypoxia could worsen Coronavirus Disease 2019 (COVID-19) patient's hypoxemia. We compared COVID-19 mortality at different altitudes. Methods: Retrospective analysis of population-level data on COVID-19 deaths was conducted in the United States (1,016 counties) and Mexico (567 municipalities). Mixed-model Poisson regression analysis of the association between altitude and COVID-19 mortality was conducted using individual-level data from 40,168 Mexican subjects with COVID-19, adjusting for multiple covariates. Results: Between January 20 and April 13, 2020, mortality rates were higher in U.S. counties located at ≥2,000 m elevation versus those located <1,500 m (12.3 vs. 3.2 per 100,000; p  < 0.001). In Mexico, between March 13 and May 13, 2020, mortality rates were higher in municipalities located at ≥2,000 m versus those located <1,500 m (5.3 vs. 3.9 per 100,000; p  < 0.001). Among Mexican subjects younger than 65 years, the risk of death was 36% higher in those living at ≥2,000 m versus those living at <1,500 m (adjusted incidence rate ratio [IRR]: 1.36; confidence interval [95% CI], 1.05-1.78; p  = 0.022). Among Mexican men, the risk of death was 31% higher at ≥2,000 m versus that at <1,500 m (adjusted IRR: 1.31; 95% CI, 1.03-1.66; p  = 0.025). No association between altitude and COVID-19 mortality was found among Mexican women or among Mexican subjects 65 years of age and older. Conclusions: Altitude is associated with COVID-19 mortality in men younger than 65 years.

Background: Patients with shockable sudden cardiac arrest (SCA; ventricular fibrillation/tachycardia) have significantly better resuscitation outcomes than do those with nonshockable rhythm (pulseless electrical activity/asystole). Heart failure (HF) increases the risk of SCA, but presenting rhythms have not been previously evaluated., Objective: We hypothesized that based on unique characteristics, HFpEF (HF with preserved ejection fraction; left ventricular ejection fraction [LVEF] ≥50%), bHFpEF (HF with borderline preserved ejection fraction; LVEF >40% and <50%), and HFrEF (HF with reduced ejection fraction; LVEF ≤40%) manifest differences in presenting rhythm during SCA., Methods: Consecutive cases of SCA with HF (age ≥18 years) were ascertained in the Oregon Sudden Unexpected Death Study (2002-2019). LVEF was obtained from echocardiograms performed before and unrelated to the SCA event. Presenting rhythms were identified from first responder reports. Logistic regression was used to evaluate the independent association of presenting rhythm with HF subtype., Results: Of 648 subjects with HF and SCA (median age 72 years; interquartile range 62-81 years), 274 had HFrEF (23.4% female), 92 had bHFpEF (35.9% female), and 282 had HFpEF (42.5% female). The rates of shockable rhythms were 44.5% (n = 122), 48.9% (n = 45), and 27.0% (n = 76) for HFrEF, bHFpEF, and HFpEF, respectively (P < .001). Compared with HFpEF, the adjusted odds ratios for shockable rhythm were 1.86 (95% confidence interval 1.27-2.74; P = .002) in HFrEF and 2.26 (95% CI 1.35-3.77; P = .002) in bHFpEF. The rates of survival to hospital discharge were 10.6% (n = 29) in HFrEF, 22.8% (n = 21) in bHFpEF, and 9.9% (n = 28) in HFpEF (P = .003)., Conclusion: The rates of shockable rhythm during SCA depend on the HF clinical subtype. Patients with bHFpEF had the highest likelihood of shockable rhythm, correlating with the highest rates of survival., (Copyright © 2020 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

With the increased prevalence of obesity and related co-morbidities, such as type 2 diabetes (T2D), worldwide, improvements in pharmacological treatments are necessary. The brain- and peripheral-cannabinoid receptor 1 (CB1R) antagonist rimonabant (RIM) has been shown to induce weight loss and improve glucose homeostasis. We have previously demonstrated that RIM promotes adipose tissue beiging and decreased adipocyte cell size, even during maintenance on a high-fat diet. Given the adverse side-effects of brain-penetrance with RIM, in this study we aimed to determine the site of action for a non-brain-penetrating CB1R antagonist AM6545. By using in vitro assays, we demonstrated the direct effects of this non-brain-penetrating CB1R antagonist on cultured adipocytes. Specifically, we showed, for the first time, that AM6545 significantly increases markers of adipose tissue beiging, mitochondrial biogenesis, and lipolysis in 3T3-L1 adipocytes. In addition, the oxygen consumption rate (OCR), consisting of baseline respiratory rate, proton leak, maximal respiratory capacity, and ATP synthase activity, was greater for cells exposed to AM6545, demonstrating greater mitochondrial uncoupling. Using a lipolysis inhibitor during real-time OCR measurements, we determined that the impact of CB1R antagonism on adipocytes is driven by increased lipolysis. Thus, our data suggest the direct role of CB1R antagonism on adipocytes does not require brain penetrance, supporting the importance of focus on peripheral CB1R antagonism pharmacology for reducing the incidence of obesity and T2D.

Background/objectives: We have recently proposed and validated a simple and accurate method to estimate whole-body fat percentage in adults, the relative fat mass (RFM), derived from the ratio of height to waist circumference. We aimed to identify RFM cutoffs to diagnose obesity based on the association between RFM and all-cause mortality., Subjects/methods: We used data from adult participants (≥20 years of age, n = 43,793) of the National Health and Nutrition Examination Survey (NHANES) 1999-2014 linked with death certificate records from the National Death Index. Optimal RFM cutoffs were determined using receiver-operating characteristic analysis (the Youden's index and the Euclidean minimum distance to the coordinate (0,1))., Results: Final dataset for analyses comprised 31,008 adults. During a median follow-up of 8.3 years (IQR, 7.6-13.7), 2,517 deaths occurred. Youden and Euclidean optimal cutoffs of baseline RFM for all-cause mortality were 40.8% and 41.6% for women, and 30.9% and 28.9% for men, respectively. Similar cutoffs were obtained using measured whole-body fat percentage by dual energy X-ray absorptiometry. Adjusting for age, BMI category, ethnicity, education level, and smoking status, the hazard ratio for mortality using Cox proportional hazard regression was 1.41 (95% CI, 1.02-1.95) among women who had an RFM of 40.0-44.9% compared with women who had an RFM <35% (P = 0.035). Among men, the hazard ratio was 1.57 (95% CI, 1.07-2.30) among those with an RFM of 30.0-34.9% compared with men who had an RFM <25% (P = 0.020). Similar adjusted hazard ratios for same RFM categories were obtained in our validation population (NHANES III, n = 12,650, median follow-up: 23.3 years): 1.42 (95% CI, 1.01-2.00) among women (P = 0.043) and 1.50 (95% CI, 1.07-2.10) among men (P = 0.021)., Conclusions: We suggest rounded RFM cutoffs of 40% for women and 30% for men to diagnose obesity and identify individuals at higher risk of death.

We evaluated the ability of the Relative Fat Mass (RFM) to estimate whole-body fat percentage among children and adolescents who participated in the National Health and Nutrition Examination Survey from 1999 through 2006 (n = 10,390). The RFM equation for adults (64 - (20 × height/waist circumference) + (12 × sex)) may be used for adolescents 15 to 19 years of age. For children and adolescents 8 to 14 years of age, we suggest a modified RFM equation, named as the RFMp (RFM pediatric): 74 - (22 × height/waist circumference) + (5 × sex). In both equations, sex equals 0 for boys and 1 for girls. RFMp was more accurate than BMI to estimate whole-body fat percentage (measured by dual energy X-ray absorptiometry, DXA) among girls (percentage of estimates that were <20% of measured body fat percentage, 88.2% vs. 85.7%; P = 0.027) and boys 8 to 14 years of age (83.4% vs. 71.0%; P < 0.001). RFM was more accurate than BMI among boys 15 to 19 years of age (82.3% vs. 73.9%; P < 0.001) but slightly less accurate among girls (89.0% vs. 92.6%; P = 0.002). Compared with BMI-for-age percentiles, RFMp had lower misclassification error of overweight or obesity (defined as a DXA-measured body fat percentage at the 85 th percentile or higher) among boys 8 to 14 years of age (6.5% vs. 7.9%; P = 0.018) but not girls (RFMp: 8.2%; BMI-for-age: 7.9%; P = 0.681). Misclassification error of overweight or obesity was similar for RFM and BMI-for-age percentiles among girls (RFM: 8.0%; BMI-for-age: 6.6%; P = 0.076) and boys 15 to 19 years of age (RFM: 6.9%; BMI-for-age: 7.8%; P = 0.11). RFMp for children and adolescents 8 to 14 years of age and RFM for adolescents 15 to 19 years of age were useful to estimate whole-body fat percentage and diagnose body fat-defined overweight or obesity.

CB1 receptor (CB1R) antagonism improves the deleterious effects of a high-fat diet (HFD) by reducing body fat mass and adipocyte cell size. Previous studies demonstrated that the beneficial effects of the CB1R antagonist rimonabant (RIM) in white adipose tissue (WAT) are partially due to an increase of mitochondria numbers and upregulation thermogenesis markers, suggesting an induction of WAT beiging. However, the molecular mechanism by which CB1R antagonism induces weight loss and WAT beiging is unclear. In this study, we probed for genes associated with beiging and explored longitudinal molecular mechanisms by which the beiging process occurs. HFD dogs received either RIM (HFD+RIM) or placebo (PL) (HFD+PL) for 16 wk. Several genes involved in beiging were increased in HFD+RIM compared with pre-fat, HFD, and HFD+PL. We evaluated lipolysis and its regulators including natriuretic peptide (NP) and its receptors ( NPRs ), β-1 and β-3 adrenergic receptor ( β1R , β3R ) genes. These genes were increased in WAT depots, accompanied by an increase in lipolysis in HFD+RIM. In addition, RIM decreased markers of inflammation and increased adiponectin receptors in WAT. We observed a small but significant increase in UCP1 ; therefore, we evaluated the newly discovered UCP1-independent thermogenesis pathway. We confirmed that SERCA2b and RYR2 , the two key genes involved in this pathway, were upregulated in the WAT. Our data suggest that the upregulation of NPRs , β-1R and β-3R , lipolysis, and SERCA2b and RYR2 may be one of the mechanisms by which RIM promotes beiging and overall the improvement of metabolic homeostasis induced by RIM.

Hyperinsulinemia, accompanied by reduced first-pass hepatic insulin extraction (FPE) and increased secretion, is a primary response to insulin resistance. Different in vivo methods are used to estimate the clearance of insulin, which is assumed to reflect FPE. We compared two methodologically different but commonly used indirect estimates with directly measured FPE in healthy dogs ( n = 9). The indirect methods were 1) metabolic clearance rate of insulin (MCR) during the hyperinsulinemic-euglycemic clamp (EGC), a steady-state method, and 2) fractional clearance rate of insulin (FCR) during the frequently sampled intravenous glucose tolerance test (FSIGT), a dynamic method. MCR was calculated as the ratio of insulin infusion rate to steady-state plasma insulin. FCR was calculated as the exponential decay rate constant of the injected insulin. Directly measured FPE is based on the difference in insulin measurements during intraportal vs. peripheral vein insulin infusions. We found a strong correlation between indirect FCR (min -1 ) and FPE (%). In contrast, we observed a poor association between MCR (ml·min -1 ·kg -1 ) and FPE (%). Our findings in canines suggest that FCR measured during FSIGT can be used to estimate FPE. However, MCR calculated during EGC appears to be a poor surrogate for FPE.

Although the β-cells secrete insulin, the liver, with its first-pass insulin extraction (FPE), regulates the amount of insulin allowed into circulation for action on target tissues. The metabolic clearance rate of insulin, of which FPE is the dominant component, is a major determinant of insulin sensitivity (SI). We studied the intricate relationship among FPE, SI, and fasting insulin. We used a direct method of measuring FPE, the paired portal/peripheral infusion protocol, where insulin is infused stepwise through either the portal vein or a peripheral vein in healthy young dogs ( n = 12). FPE is calculated as the difference in clearance rates (slope of infusion rate vs. steady insulin plot) between the paired experiments. Significant correlations were found between FPE and clamp-assessed SI ( r s = 0.74), FPE and fasting insulin ( r s = -0.64), and SI and fasting insulin ( r s = -0.67). We also found a wide variance in FPE (22.4-77.2%; mean ± SD 50.4 ± 19.1) that is reflected in the variability of plasma insulin (48.1 ± 30.9 pmol/L) and SI (9.4 ± 5.8 × 10 4 dL · kg -1 · min -1 · [pmol/L] -1 ). FPE could be the nexus of regulation of both plasma insulin and SI., (© 2018 by the American Diabetes Association.)

High whole-body fat percentage is independently associated with increased mortality. We aimed to identify a simple anthropometric linear equation that is more accurate than the body mass index (BMI) to estimate whole-body fat percentage among adult individuals. National Health and Nutrition Examination Survey (NHANES) 1999-2004 data (n = 12,581) were used for model development and NHANES 2005-2006 data (n = 3,456) were used for model validation. From the 365 anthropometric indices generated, the final selected equation was as follows: 64 - (20 × height/waist circumference) + (12 × sex), named as the relative fat mass (RFM); sex = 0 for men and 1 for women. In the validation dataset, compared with BMI, RFM better predicted whole-body fat percentage, measured by dual energy X-ray absorptiometry (DXA), among women and men. RFM showed better accuracy than the BMI and had fewer false negative cases of body fat-defined obesity among women and men. RFM reduced total obesity misclassification among all women and all men and, overall, among Mexican-Americans, European-Americans and African-Americans. In the population studied, the suggested RFM was more accurate than BMI to estimate whole-body fat percentage among women and men and improved body fat-defined obesity misclassification among American adult individuals of Mexican, European or African ethnicity.

Activation of the sympathetic nervous system (SNS) constitutes a putative mechanism of obesity-induced insulin resistance. Thus, we hypothesized that inhibiting the SNS by using renal denervation (RDN) will improve insulin sensitivity (S I ) in a nonhypertensive obese canine model. S I was measured using euglycemic-hyperinsulinemic clamp (EGC), before (week 0 [w0]) and after 6 weeks of high-fat diet (w6-HFD) feeding and after either RDN (HFD + RDN) or sham surgery (HFD + sham). As expected, HFD induced insulin resistance in the liver (sham 2.5 ± 0.6 vs. 0.7 ± 0.6 × 10 -4 dL ⋅ kg -1 ⋅ min -1 ⋅ pmol/L - 1 at w0 vs. w6-HFD [P < 0.05], respectively; HFD + RDN 1.6 ± 0.3 vs. 0.5 ± 0.3 × 10 -4 dL ⋅ kg -1 ⋅ min -1 ⋅ pmol/L -1 at w0 vs. w6-HFD [P < 0.001], respectively). In sham animals, this insulin resistance persisted, yet RDN completely normalized hepatic S I in HFD-fed animals (1.8 ± 0.3 × 10 -4 dL ⋅ kg -1 ⋅ min -1 ⋅ pmol/L -1 at HFD + RDN [P < 0.001] vs. w6-HFD, [P not significant] vs. w0) by reducing hepatic gluconeogenic genes, including G6Pase, PEPCK, and FOXO1. The data suggest that RDN downregulated hepatic gluconeogenesis primarily by upregulating liver X receptor α through the natriuretic peptide pathway. In conclusion, bilateral RDN completely normalizes hepatic S I in obese canines. These preclinical data implicate a novel mechanistic role for the renal nerves in the regulation of insulin action specifically at the level of the liver and show that the renal nerves constitute a new therapeutic target to counteract insulin resistance., (© 2016 by the American Diabetes Association.)

Aims/hypothesis: Endothelial cells (ECs) play an essential role in pancreatic organogenesis. We hypothesise that effective in vitro interactions between human microvascular endothelial cells (HMECs) and human pluripotent stem cells (hPSCs) results in the generation of functional pancreatic beta cells., Methods: Embryoid bodies (EBs) derived from hPSCs were cultured alone (controls) or with ECs in collagen gels. Subsequently, cells were analysed for pancreatic beta cell markers, and then isolated and expanded. Insulin secretion in response to glucose was evaluated in vitro by static and dynamic (perifusion) assays, and in vivo by EB transplantation into immunodeficient mice., Results: Co-cultured EBs had a higher expression of mature beta cells markers and enhanced insulin secretion in vitro, compared with controls. In mice, transplanted EBs had higher levels of human C-peptide secretion with a significant reduction in hyperglycaemia after the selective destruction of native pancreatic beta cells. In addition, there was significant in vitro upregulation of bone morphogenetic proteins 2 and 4 (BMP-2, 4) in co-cultured cells, compared with controls., Conclusions/interpretation: ECs provide essential signalling in vitro, such as activation of the BMP pathway, for derivation of functional insulin-producing beta cells from hPSCs.

Background: Exenatide's effects on glucose metabolism have been studied extensively in diabetes but not in pre-diabetes., Objective: We examined the chronic effects of exenatide alone on glucose metabolism in pre-diabetic canines., Design and Methods: After 10 weeks of high-fat diet (HFD), adult dogs received one injection of streptozotocin (STZ, 18.5 mg/kg). After induction of pre-diabetes, while maintained on HFD, animals were randomized to receive either exenatide (n = 7) or placebo (n = 7) for 12 weeks. β-Cell function was calculated from the intravenous glucose tolerance test (IVGTT, expressed as the acute insulin response, AIRG), the oral glucose tolerance test (OGTT, insulinogenic index) and the graded-hyperglycemic clamp (clamp insulinogenic index). Whole-body insulin sensitivity was assessed by the IVGTT. At the end of the study, pancreatic islets were isolated to assess β-cell function in vitro., Results: OGTT: STZ caused an increase in glycemia at 120 min by 22.0% (interquartile range, IQR, 31.5%) (P = 0.011). IVGTT: This protocol also showed a reduction in glucose tolerance by 48.8% (IQR, 36.9%) (P = 0.002). AIRG decreased by 54.0% (IQR, 40.7%) (P = 0.010), leading to mild fasting hyperglycemia (P = 0.039). Exenatide, compared with placebo, decreased body weight (P<0.001) without altering food intake, fasting glycemia, insulinemia, glycated hemoglobin A1c, or glucose tolerance. Exenatide, compared with placebo, increased both OGTT- (P = 0.040) and clamp-based insulinogenic indexes (P = 0.016), improved insulin secretion in vitro (P = 0.041), but had no noticeable effect on insulin sensitivity (P = 0.405)., Conclusions: In pre-diabetic canines, 12-week exenatide treatment improved β-cell function but not glucose tolerance or insulin sensitivity. These findings demonstrate partial beneficial metabolic effects of exenatide alone on an animal model of pre-diabetes.

Objective: To determine the association between altitude and obesity in a nationally representative sample of the Peruvian adult population., Methods: This is a cross-sectional analysis of publicly available data from the Food and Nutrition National Center (CENAN, Peru), period 2009-2010. The Prevalence ratio of obesity and abdominal obesity was determined as a measure of association. Obesity and abdominal obesity were diagnosed based on direct anthropometric measurements., Results: The final data set consisted of 31,549 individuals ≥20 years old. The prevalence ratio of obesity was as follows: 1.00 between 0 and 499 m (reference category), 1.00 (95% confidence interval 0.87-1.16) between 500-1,499 m, 0.74 (0.63-0.86) between 1,500-2,999 m, and 0.54 (0.45-0.64) at ≥3,000 m, adjusting for age, sex, self-reported physical activity, out-migration rate, urbanization, poverty, education, and geographical latitude and longitude. In the same order, the adjusted prevalence ratio of abdominal obesity was 1.00, 1.01 (0.94-1.07), 0.93 (0.87-0.99), and 0.89 (0.82-0.95), respectively. We found an interaction between altitude and sex and between altitude and age (P < 0.001, for both interactions) on the association with obesity and abdominal obesity., Conclusions: Among Peruvian adult individuals, we found an inverse association between altitude and obesity, adjusting for multiple covariates. This adjusted association varied by sex and age., (© 2016 The Obesity Society.)

The improvement of hepatic insulin sensitivity by the cannabinoid receptor 1 (CB1R) antagonist rimonabant (RIM) has been recently been reported to be due to upregulation of adiponectin. Several studies demonstrated that improvement in insulin clearance accompanies the enhancement of hepatic insulin sensitivity. However, the effects of RIM on hepatic insulin clearance (HIC) have not been fully explored. The aim of this study was to explore the molecular mechanism(s) by which RIM affects HIC, specifically to determine whether upregulation of liver adiponectin receptors (ADRs) and other key genes regulated by adiponectin mediate the effects. To induce insulin resistance in skeletal muscle and liver, dogs were fed a hypercaloric high-fat diet (HFD) for 6 wk. Thereafter, while still maintained on a HFD, animals received RIM (HFD+RIM; n = 11) or placebo (HFD+PL; n = 9) for an additional 16 wk. HIC, calculated as the metabolic clearance rate (MCR), was estimated from the euglycemic-hyperinsulinemic clamp. The HFD+PL group showed a decrease in MCR; in contrast, the HFD+RIM group increased MCR. Consistently, the expression of genes involved in HIC, CEACAM-1 and IDE, as well as gene expression of liver ADRs, were increased in the HFD+RIM group, but not in the HFD+PL group. We also found a positive correlation between CEACAM-1 and the insulin-degrading enzyme IDE with ADRs. Interestingly, expression of liver genes regulated by adiponectin and involved in lipid oxidation were increased in the HFD+RIM group. We conclude that in fat-fed dogs RIM enhances HIC, which appears to be linked to an upregulation of the adiponectin pathway., (Copyright © 2015 the American Physiological Society.)

Background: Obesity has been associated with elevated plasma anandamide levels. In addition, anandamide has been shown to stimulate insulin secretion in vitro, suggesting that anandamide might be linked to hyperinsulinemia., Objective: To determine whether high-fat diet-induced insulin resistance increases anandamide levels and potentiates the insulinotropic effect of anandamide in isolated pancreatic islets., Design and Methods: Dogs were fed a high-fat diet (n = 9) for 22 weeks. Abdominal fat depot was quantified by MRI. Insulin sensitivity was assessed by the euglycemic-hyperinsulinemic clamp. Fasting plasma endocannabinoid levels were analyzed by liquid chromatography-mass spectrometry. All metabolic assessments were performed before and after fat diet regimen. At the end of the study, pancreatic islets were isolated prior to euthanasia to test the in vitro effect of anandamide on islet hormones. mRNA expression of cannabinoid receptors was determined in intact islets. The findings in vitro were compared with those from animals fed a control diet (n = 7)., Results: Prolonged fat feeding increased abdominal fat content by 81.3±21.6% (mean±S.E.M, P<0.01). In vivo insulin sensitivity decreased by 31.3±12.1% (P<0.05), concomitant with a decrease in plasma 2-arachidonoyl glycerol (from 39.1±5.2 to 15.7±2.0 nmol/L) but not anandamide, oleoyl ethanolamide, linoleoyl ethanolamide, or palmitoyl ethanolamide. In control-diet animals (body weight: 28.8±1.0 kg), islets incubated with anandamide had a higher basal and glucose-stimulated insulin secretion as compared with no treatment. Islets from fat-fed animals (34.5±1.3 kg; P<0.05 versus control) did not exhibit further potentiation of anandamide-induced insulin secretion as compared with control-diet animals. Glucagon but not somatostatin secretion in vitro was also increased in response to anandamide, but there was no difference between groups (P = 0.705). No differences in gene expression of CB1R or CB2R between groups were found., Conclusions: In canines, high-fat diet-induced insulin resistance does not alter plasma anandamide levels or further potentiate the insulinotropic effect of anandamide in vitro.

Most of the literature related to high altitude medicine is devoted to the short-term effects of high-altitude exposure on human physiology. However, long-term effects of living at high altitudes may be more important in relation to human disease because more than 400 million people worldwide reside above 1500 m. Interestingly, individuals living at higher altitudes have a lower fasting glycemia and better glucose tolerance compared with those who live near sea level. There is also emerging evidence of the lower prevalence of both obesity and diabetes at higher altitudes. The mechanisms underlying improved glucose control at higher altitudes remain unclear. In this review, we present the most current evidence about glucose homeostasis in residents living above 1500 m and discuss possible mechanisms that could explain the lower fasting glycemia and lower prevalence of obesity and diabetes in this population. Understanding the mechanisms that regulate and maintain the lower fasting glycemia in individuals who live at higher altitudes could lead to new therapeutics for impaired glucose homeostasis.

Objectives: To determine whether a selective increase of visceral adipose tissue content will result in insulin resistance., Methods: Sympathetic denervation of the omental fat was performed under general inhalant anesthesia by injecting 6-hydroxydopamine in the omental fat of lean mongrel dogs (n = 11). In the conscious animal, whole-body insulin sensitivity was assessed by the minimal model (SI ) and the euglycemic hyperinsulinemic clamp (SICLAMP ). Changes in abdominal fat were monitored by magnetic resonance. All assessments were determined before (Wk0) and 2 weeks (Wk2) after denervation. Data are medians (upper and lower interquartile)., Results: Denervation of omental fat resulted in increased percentage (and content) of visceral fat [Wk0: 10.2% (8.5-11.4); Wk2: 12.4% (10.4-13.6); P < 0.01]. Abdominal subcutaneous fat remained unchanged. However, no changes were found in SI [Wk0: 4.7 (mU/l)(-1) min(-1) (3.1-8.8); Wk2: 5.3 (mU/l)(-1) min(-1) (4.5-7.2); P = 0.59] or SICLAMP [Wk0: 42.0 × 10(-4) dl kg(-1) min(-1) (mU/l)(-1) (41.0-51.0); Wk2: 40.0 × 10(-4) dl kg(-1) min(-1) (mU/l) (-1) (34.0-52.0); P = 0.67]., Conclusions: Despite a selective increase in visceral adiposity in dogs, insulin sensitivity in vivo did not change, which argues against the concept that accumulation of visceral adipose tissue contributes to insulin resistance., (© 2014 The Obesity Society.)

The hepatoportal area is an important glucohomeostatic metabolic sensor, sensing hypoglycemia, hyperglycemia, and hormones such as glucagon-like peptide-1 (GLP-1). We have reported previously that activation of hepatoportal sensors by intraportal infusion of glucose and GLP-1 or by subcutaneous administration of GLP-1 receptor activator exenatide and of intraportal glucose improved glycemia independent of corresponding changes in pancreatic hormones. It is not clear whether this effect is mediated via the portal vein (PV) or by direct action on the liver itself. To test whether receptors in the PV mediate exenatide's beneficial effect on glucose tolerance, we performed 1) paired oral glucose tolerance tests (OGTT) with and without exenatide and 2) intravenous glucose tolerance tests before and after PV denervation in canines. Denervation of the portal vein affected oral glucose tolerance; post-denervation (POST-DEN) OGTT glucose and insulin AUC were 50% higher than before denervation (P = 0.01). However, portal denervation did not impair exenatide's effect to improve oral glucose tolerance (exenatide effect: 48 ± 12 mmol·l⁻¹·min before vs. 64 ± 26 mmol·l⁻¹·min after, P = 0.67). There were no changes in insulin sensitivity or secretion during IVGTTs. Portal vein sensing might play a role in controlling oral glucose tolerance during physiological conditions but not in pharmacological activation of GLP-1 receptors by exenatide., (Copyright © 2014 the American Physiological Society.)

Objective: To determine whether geographical elevation is inversely associated with diabetes, while adjusting for multiple risk factors., Methods: This is a cross-sectional analysis of publicly available online data from the Behavioral Risk Factor Surveillance System, 2009. Final dataset included 285,196 US adult subjects. Odds ratios were obtained from multilevel mixed-effects logistic regression analysis., Results: Among US adults (≥20 years old), the odds ratio for diabetes was 1.00 between 0 and 499 m of altitude (reference), 0.95 (95% confidence interval, 0.90-1.01) between 500 and 1,499 m, and 0.88 (0.81-0.96) between 1,500 and 3,500 m, adjusting for age, sex, body mass index, ethnicity, self-reported fruit and vegetable consumption, self-reported physical activity, current smoking status, level of education, income, health status, employment status, and county-level information on migration rate, urbanization, and latitude. The inverse association between altitude and diabetes in the US was found among men [0.84 (0.76-0.94)], but not women [1.09 (0.97-1.22)]., Conclusions: Among US adults, living at high altitude (1,500-3,500 m) is associated with lower odds of having diabetes than living between 0 and 499 m, while adjusting for multiple risk factors. Our findings suggest that geographical elevation may be an important factor linked to diabetes., (© 2014 The Obesity Society.)

A recent study published by Muslikhov et al. (Biochemistry (Moscow), 79, 435439 (2014)) showed that arachi donic acid increases cytosolic Ca2+ concentrations in C2C12 skeletal myotubes mainly via activation of the ryanodine (RY) receptor 1. These results are consistent with the data from another study demonstrating that arachidonic acid targets RY receptor 2 in clonal and primary pancreatic βcells (Woolcott et al., 2006). A novel and intriguing finding by Muslikhov’s group is that arachidonic acid also appears to activate the twopore ion channel (TPC), suggesting that arachidonic acid could be a mediator in the interaction between TPCs and RY receptors.

Objective: Insulin resistance is a powerful risk factor for Type 2 diabetes and a constellation of chronic diseases, and is most commonly associated with obesity. We examined if factors other than obesity are more substantial predictors of insulin sensitivity under baseline, nonstimulated conditions., Methods: Metabolic assessment was performed in healthy dogs (n = 90). Whole-body sensitivity from euglycemic clamps (SICLAMP ) was the primary outcome variable, and was measured independently by IVGTT (n = 36). Adiposity was measured by MRI (n = 90), and glucose-stimulated insulin response was measured from hyperglycemic clamp or IVGTT (n = 86 and 36, respectively)., Results: SICLAMP was highly variable (5.9-75.9 dl/min per kg per μU/ml). Despite narrow range of body weight (mean, 28.7 ± 0.3 kg), adiposity varied approximately eight-fold and was inversely correlated with SICLAMP (P < 0.025). SICLAMP was negatively associated with fasting insulin, but most strongly associated with insulin clearance. Clearance was the dominant factor associated with sensitivity (r = 0.53, P < 0.00001), whether calculated from clamp or IVGTT., Conclusions: These data suggest that insulin clearance contributes substantially to insulin sensitivity, and may be pivotal in understanding the pathogenesis of insulin resistance. We propose the hyperinsulinemia due to reduction in insulin clearance is responsible for insulin resistance secondary to changes in body weight., (Copyright © 2013 The Obesity Society.)

A major issue of in the treatment of diabetes is the risk of hypoglycemia. Hypoglycemia is detected both centrally and peripherally in the porto-hepatic area. The portal locus for hypoglycemic detection was originally described using the "local irrigation of the liver" approach in a canine model. Further work using portal vein denervation (DEN) in a rodent model characterized portal hypoglycemic sensing in detail. However, recent controversy about the relevance of rodent findings to large animals and humans prompted us to investigate the effect of portal DEN on the hypoglycemic response in the canine, a species with multiple similarities to human glucose homeostasis. Hypoglycemic hyperinsulinemic clamps were performed in male canines, before (PRE) and after (POST) portal vein DEN or sham surgery (CON, control). Insulin (30 pmol/kg·min) and glucose (variable) were infused to slowly decrease systemic glycemia to 50 mg/dL over 160 minutes. The average plasma glucose during clamp steady state was: 2.9 ± 0.1 mmol DEN-PRE, 2.9 ± 0.2 mmol DEN-POST, 2.9 ± 0.1 mmol CON-PRE, and 2.8 ± 0.0 mmol CON-POST. There were no significant differences in plasma insulin between DEN and CON, PRE and POST experiments. The epinephrine response to hypoglycemia was reduced by 62% in DEN but not in CON. Steady-state cortisol was 46% lower after DEN but not after CON. Our study shows, in a large animal model, that surgical disconnection of the portal vein from the afferent pathway of the hypoglycemic counterregulatory circuitry results in a substantial suppression of the epinephrine response and a significant impact on cortisol response. These findings directly demonstrate an essential role for the portal vein in sensing hypoglycemia and relating glycemic information to the central nervous system.

The endocannabinoid system is highly implicated in the development of insulin resistance associated with obesity. It has been shown that antagonism of the CB(1) receptor improves insulin sensitivity (S(I)). However, it is unknown whether this improvement is due to the direct effect of CB(1) blockade on peripheral tissues or secondary to decreased fat mass. Here, we examine in the canine dog model the longitudinal changes in S(I) and fat deposition when obesity was induced with a high-fat diet (HFD) and animals were treated with the CB(1) antagonist rimonabant. S(I) was assessed (n = 20) in animals fed a HFD for 6 wk to establish obesity. Thereafter, while HFD was continued for 16 additional weeks, animals were divided into two groups: rimonabant (1.25 mg·kg(-1)·day(-1) RIM; n = 11) and placebo (n = 9). Euglycemic hyperinsulinemic clamps were performed to evaluate changes in insulin resistance and glucose turnover before HFD (week -6) after HFD but before treatment (week 0) and at weeks 2, 6, 12, and 16 of treatment (or placebo) + HFD. Magnetic resonance imaging was performed to determine adiposity- related changes in S(I). Animals developed significant insulin resistance and increased visceral and subcutaneous adiposity after 6 wk of HFD. Treatment with RIM resulted in a modest decrease in total trunk fat with relatively little change in peripheral glucose uptake. However, there was significant improvement in hepatic insulin resistance after only 2 wk of RIM treatment with a concomitant increase in plasma adiponectin levels; both were maintained for the duration of the RIM treatment. CB(1) receptor antagonism appears to have a direct effect on hepatic insulin sensitivity that may be mediated by adiponectin and independent of pronounced reductions in body fat. However, the relatively modest effect on peripheral insulin sensitivity suggests that significant improvements may be secondary to reduced fat mass.

Objectives: The canine model has been used extensively to improve the human pancreatic islet isolation technique. At the functional level, dog islets show high similarity to human islets and thus can be a helpful tool for islet research. We describe and compare 2 manual isolation methods, M1 (initial) and M2 (modified), and analyze the variables associated with the outcomes, including islet yield, purity, and glucose-stimulated insulin secretion (GSIS)., Methods: Male mongrel dogs were used in the study. M2 (n = 7) included higher collagenase concentration, shorter digestion time, faster shaking speed, colder purification temperature, and higher differential density gradient than M1 (n = 7)., Results: Islet yield was similar between methods (3111.0 ± 309.1 and 3155.8 ± 644.5 islets/g, M1 and M2, respectively; P = 0.951). Pancreas weight and purity together were directly associated with the yield (adjusted R(2) = 0.61; P = 0.002). Purity was considerably improved with M2 (96.7% ± 1.2% vs 75.0% ± 6.3%; P = 0.006). M2 improved GSIS (P = 0.021). Independently, digestion time was inversely associated with GSIS., Conclusions: We describe an isolation method (M2) to obtain a highly pure yield of dog islets with adequate β-cell glucose responsiveness. The isolation variables associated with the outcomes in our canine model confirm previous reports in other species, including humans.

Adipocyte size plays a key role in the development of insulin resistance. We examined longitudinal changes in adipocyte size and distribution in visceral (VIS) and subcutaneous (SQ) fat during obesity-induced insulin resistance and after treatment with CB-1 receptor antagonist, rimonabant (RIM) in canines. We also examined whether adipocyte size and/or distribution is predictive of insulin resistance. Adipocyte morphology was assessed by direct microscopy and analysis of digital images in previously studied animals 6 weeks after high-fat diet (HFD) and 16 weeks of HFD + placebo (PL; n = 8) or HFD + RIM (1.25 mg/kg/day; n = 11). At 6 weeks, mean adipocyte diameter increased in both depots with a bimodal pattern only in VIS. Sixteen weeks of HFD+PL resulted in four normally distributed cell populations in VIS and a bimodal pattern in SQ. Multilevel mixed-effects linear regression with random-effects model of repeated measures showed that size combined with share of adipocytes >75 µm in VIS only was related to hepatic insulin resistance. VIS adipocytes >75 µm were predictive of whole body and hepatic insulin resistance. In contrast, there was no predictive power of SQ adipocytes >75 µm regarding insulin resistance. RIM prevented the formation of large cells, normalizing to pre-fat status in both depots. The appearance of hypertrophic adipocytes in VIS is a critical predictor of insulin resistance, supporting the deleterious effects of increased VIS adiposity in the pathogenesis of insulin resistance.

We investigated whether rimonabant, a type 1 cannabinoid receptor antagonist, reduces visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in dogs maintained on a hypercaloric high-fat diet (HHFD). To determine whether energy expenditure contributed to body weight changes, we also calculated resting metabolic rate. Twenty male dogs received either rimonabant (1.25 mg.kg(-1).day(-1), orally; n = 11) or placebo (n = 9) for 16 wk, concomitant with a HHFD. VAT, SAT, and nonfat tissue were measured by magnetic resonance imaging. Resting metabolic rate was assessed by indirect calorimetry. By week 16 of treatment, rimonabant dogs lost 2.5% of their body weight (P = 0.029), whereas in placebo dogs body weight increased by 6.2% (P < 0.001). Rimonabant reduced food intake (P = 0.027), concomitant with a reduction of SAT by 19.5% (P < 0.001). In contrast with the VAT increase with placebo (P < 0.01), VAT did not change with rimonabant. Nonfat tissue remained unchanged in both groups. Body weight loss was not associated with either resting metabolic rate (r(2) = 0.24; P = 0.154) or food intake (r(2) = 0.24; P = 0.166). In conclusion, rimonabant reduced body weight together with a reduction in abdominal fat, mainly because of SAT loss. Body weight changes were not associated with either resting metabolic rate or food intake. The findings provide evidence of a peripheral effect of rimonabant to reduce adiposity and body weight, possibly through a direct effect on adipose tissue.

It is known that residents at high altitude (HA) have a lower basal glycemia than residents at sea level (SL). However, whether such a difference is maintained throughout the full day remains unknown. We compared 12-h blood glucose profiles from 10 healthy males native residents at HA (3250 m) and 8 male residents at SL. Glucose profile at HA was lower throughout the glucose monitoring than that at SL (mean profile: 50.6 +/- 3.7 and 73.4 +/- 4.0 mg/dL, respectively; p < 0.001). Basal and postprandial insulin and triacylglycerol values were similar in both groups. In conclusion, HA natives resident have a lower blood glucose profile than SL residents throughout 12-h continuous monitoring.

Pancreatic beta-cells have ryanodine receptors but little is known about their physiological regulation. Previous studies have shown that arachidonic acid releases Ca(2+) from intracellular stores in beta-cells but the identity of the channels involved in the Ca(2+) release has not been elucidated. We studied the mechanism by which arachidonic acid induces Ca(2+) concentration changes in pancreatic beta-cells. Cytosolic free Ca(2+) concentration was measured in fura-2-loaded INS-1E cells and in primary beta-cells from Wistar rats. The increase of cytosolic Ca(2+) concentration induced by arachidonic acid (150microM) was due to both Ca(2+) release from intracellular stores and influx of Ca(2+) from extracellular medium. 5,8,11,14-Eicosatetraynoic acid, a non-metabolizable analogue of arachidonic acid, mimicked the effect of arachidonic acid, indicating that arachidonic acid itself mediated Ca(2+) increase. The Ca(2+) release induced by arachidonic acid was from the endoplasmic reticulum since it was blocked by thapsigargin. 2-Aminoethyl diphenylborinate (50microM), which is known to inhibit 1,4,5-inositol-triphosphate-receptors, did not block Ca(2+) release by arachidonic acid. However, ryanodine (100microM), a blocker of ryanodine receptors, abolished the effect of arachidonic acid on Ca(2+) release in both types of cells. These observations indicate that arachidonic acid is a physiological activator of ryanodine receptors in beta-cells.

Background: Persons living at high altitude (exposed to hypoxia) have a greater number of coronary and peripheral branches in the heart than persons living at sea level. In this study we investigated the effect of intermittent hypobaric hypoxia on myocardial perfusion in patients with coronary heart disease., Methods and Results: We studied 6 male patients (aged>or=53 years) with severe stable coronary heart disease. All patients were born at sea level and lived in that environment. They underwent 14 sessions of exposure to intermittent hypobaric hypoxia (equivalent to a simulated altitude of 4200 m). Myocardial perfusion was assessed at baseline and after treatment with hypoxia by use of exercise perfusion imaging with technetium 99m sestamibi. After the sessions of hypoxia, myocardial perfusion was significantly improved. The summed stress score for hypoperfusion, in arbitrary units, decreased from 9.5+ to 4.5+ after treatment (P=.036). There was no evidence of impairment of myocardial perfusion in any patient after treatment., Conclusions: Intermittent hypobaric hypoxia improved myocardial perfusion in patients with severe coronary heart disease. Though preliminary, our results suggest that exposure to intermittent hypobaric hypoxia could be an alternative for the management of patients with chronic coronary heart disease.