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. K E Y W O R D Schronic kidney disease, diabetes, obesity, oxidative stress, renin-angiotensin system | 423 RODRIGUEZ Et al.

Caloric restriction, among other behavioral interventions, has demonstrated benefits on improving glycemic control in obesity-associated diabetic subjects. However, an acute and severe intervention without proper maintenance could reverse the initial benefits, with additional metabolic derangements. To assess the effects of an acute caloric restriction in a metabolic syndrome model, a cohort of 15-week old Long Evans Tokushima Otsuka (LETO) and Otsuka Long Evans Tokushima Fatty (OLETF) rats were calorie restricted (CR: 50% × 10 days) with or without a 10-day body mass (BM) recovery period, along with their respective ad libitum controls. An oral glucose tolerance test (oGTT) was performed after CR and BM recovery. Both strains had higher rates of mass gain during recovery vs. ad lib controls; however, the regain was partial (ca. 50% of ad lib controls) over the measurement period. Retroperitoneal and epididymal adipose masses decreased 30% (8.8 g, P < 0.001) in OLETF; however, this loss only accounted for 11.5% of the total BM loss. CR decreased blood glucose AUC 16% in LETO and 19% in OLETF, without significant decreases in insulin. Following CR, hepatic expression of the gluconeogenic enzyme, PEPCK, was reduced 55% in OLETF compared to LETO, and plasma triglycerides (TG) decreased 86%. Acute CR induced improvements in glucose tolerance and TG suggestive of improvements in metabolism; however, partial recovery of BM following CR abolished the improvement in glucose tolerance. The present study highlights the importance of proper maintenance of BM after CR as only partial recovery of the lost BM reversed benefits of the initial mass loss.

Inhibition of sodium‐glucose cotransporter 2 (SGLT2), a transporter highly expressed in the renal proximal tubules, decreases plasma glucose by increasing urinary excretion. For this reason, SGLT2 inhibitors are emerging as a novel therapy for T2DM [1]. When used in monotherapy, these inhibitors present low risk for hypoglycemia, preserved islet mass, and improved insulin sensitivity [2]. Current data suggest improvement in cardiovascular health as well; however, the use of this drug is not advised in the event of low‐carbohydrate diets, extreme insulin deficiency or cachexia [3]. Our hypothesis is that a mild caloric restriction (30%) combined with SGLT2i treatment, will improve metabolic syndrome and SBP without hypoglycemia, insulin deficiency, or cachexia.Fourteen lean Long Evans Tokushima Otsuka (LETO) rats, and twenty‐eight obese, insulin resistant Otsuka Long Evans Tokushima Fatty rats (OLETF) of 10 weeks of age were fed ad libidum during 4 weeks. After that time, they were randomly assigned into A) LETO (n=14), B) OLETF (n=14) and C) OLETF with SGLT2i (n=14; 10 mg/kg/d of luseogliflozin × 2 wks) groups. After the 2 weeks, the three groups were divided into either ad lib control (n=7) or caloric restriction (CR; n=7; 2 wks), which were given 70% food intake of the control groups. After the 2 wks CR, 24 hr urine samples were collected, rats were subjected to an oral glucose tolerance test (oGTT), and dissected 3 days later.Mass (Fig. 1) and food intake were recorded daily. Systolic, diastolic, and mean arterial pressure were measured by tail‐cuff plethysmography twice per week (n=6). Blood glucose and plasma insulin were measured at 0, 5, 10, 30, 60 and 120 min during oGTT. Both AUC for glucose and insulin concentrations were multiplied to obtain the IRI (Fig. 2)Mean mass for OLETF Control and OLETF SGLT2i increased without significant differences, and all CR groups maintained their baseline body mass. Differences in blood pressure were significant between LETO and OLETF, but not among groups. Fasting glucose increased with CR in both LETO (69±3 vs 74±3 mg/dl), and OLETF (93±5 vs 95±3 mg/dl), but decreased in OLETF SGLT2i (105±3 vs 93±6 mg/dl). Mean IRI in OLETF SGLT2i was higher than OLETF fed ad lib (13.1±1.4 vs 12.5±0.8 RI), but significantly lower in CR (14.5±1.0 vs 9.7±0.9 RI). 24h glucose urine excretion decreased 41.3% in CR vs Control in OLETF SGLT2i. Mean plasma triglyceride concentrations were significantly different between strains, but not among OLETF groups.In conclusion, IR was ameliorated when SGLT2 was combined with CR, but had no profound effect on SBP or plasma triglycerides. CR, concomitant to SGLT2i, resulted in an unexpected decrease in urinary glucose excretion without fasting hypoglycemia. These results suggest the possibility of a relatively safe and more efficient treatment combining SGLT2i and CR.Support or Funding InformationWe thank the graduate students and staff from the Department of Pharmacology at Kagawa University for their assistance during this study. This research was funded by a doctoral fellowship from the University of California Institute for Mexico and the United States and Mexico's National Council for Science and Technology (UC MEXUS‐CONACYT) and a Minorities Health and Health Disparities International Research Training Fellowship.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Mitochondria provide energy to the cells, making the task of mitochondrial recycling highly important. Impairments in mitochondrial number and function can lead to dysregulation of cellular metabolism and disrupted capacity to maintain homeostasis. The Parkin gene codes for the protein, Parkin, which is a component of the Parkin/PINK1 pathway that helps regulate mitophagy. An impairment in the Parkin gene may also results in nonfunctional mitochondria, potentially leading to many diseases such as type two diabetes mellitus and cardiovascular disease. Recent studies suggest that Parkin expression is downregulated during insulin resistance. To address the hypothesis that insulin resistance downregulates Parkin in the heart, a piece of the left ventricle of the hearts of 4 groups of rats were extracted: (1) Long Evans Tokushima Otsuka (LETO), (2) Otsuka Long‐Evans Tokushima Fatty (OLETF), (3) LETO with caloric restriction, and (4) OLETF with caloric restriction. Extracted Parkin from the hearts of each group was measured by Western blot. Because Parkin expression is downregulated with insulin resistance, we anticipated lower levels of express in the insulin resistant, OLETF rats compared to LETO, and that caloric restriction would restore Parkin expression in the OLETF rats. Parkin protein expression was 71% lower in OLETF than LETO. While the 16% increase in expression in caloric restricted LETO group was not statistically significant, the expression increased nearly 7.5‐fold with caloric restriction in OLETF group compared to the ad lib OLETF group. The data suggest that the benefits of CR on CV function and health go beyond the potential benefits of mass loss (usually adiposity) but include cellular energetics and metabolism in the heart of insulin resistant rats.Support or Funding InformationThe STRIDE Fellowship is supported by the American Physiological Society and a grant from the National Heart, Lung and Blood Institute (NHLBI; 1 R25 HL115473‐01).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The adipokine leptin has an important role in regulating body mass, and high concentrations lead to a resistance in target organs (e.g. β‐cells). Adiponectin, on the other hand, is considered antidiabetic and is inversely correlated to adipose tissue mass, which is reduced via caloric restriction (CR). SGLT2 transporter expression in the kidney is increased in diabetic conditions, leading to a higher glucose reabsorption and maintained hyperglycemia. During conditions of caloric restriction, increased hepatic PEPCK‐C expression contributes to an increase in hepatic gluconeogenesis via production of G3P. Our goal was to assess the effect of acute CR on adipokine profile and glucose metabolism in an obese, insulin resistant, animal model.Twenty‐eight lean LETO and 28 obese, insulin resistant OLETF rats were separated in two ad libidum food control groups (n=14 each), two CR groups, and two partial recovery (PR) groups (n=7 each). All groups were fed ad libidum for 4 weeks. After that time CR and PR groups were fed half the mean food intake of the ad libidum LETO group for 10 days, after which CR were dissected. The PR groups were fed ad libidum for 7 days and dissected.Blood was collected during dissection after 12 h fasting, and serum was preserved for measuring adipokines. Both leptin and adiponectin were measured by commercially available ELISA kits. SGLT2 and PEPCK‐C expression were measured by Western Blot from the kidney cortex and liver, using Ponceau stain as a loading control.Mean serum leptin was higher in OLETF (P=0.038) than LETO, but decreased 3‐fold after CR and recovered below threshold levels after PR (8.6 ± 1.2 in PR vs 15.4 ± 4.5 ng/ml Control). Serum adiponectin remained unchanged in both strains after CR, but increased after PR (2.3 ± 0.2 To 3.7 ± 0.2, P<0.001 in LETO and 3.3 ± 0.2 to 3.9 ± 0.1 μg/ml, P=0.05 in OLETF). Baseline leptin‐adiponectin ratio was 3‐fold higher in OLETF vs LETO. However, the ratio decreased 2‐fold in LETO and 3‐fold in OLETF (P<0.001) after CR (Fig. 1)Mean SGLT2 expression in the kidney increased after CR in both strains (21%, in LETO and 40%, in OLETF), and that increase was maintained in OLETF, but not for LETO, after PR (Fig. 2). Changes in PEPCK‐C expression in LETO were not detectable; however, expression in OLETF was higher than LETO (P<0.001) and decreased after CR (222% to 178%) and even further after PR (to 124%) (Fig. 3). Nonetheless, mean expression for PR control in OLETF is half of CR control, suggesting a high variability within the strain.In conclusion, an acute caloric restriction improves adipokine profile in both strains even after PR, suggesting a protective effect by increased expression of adiponectin with reduced fat mass. Moreover, glucose reabsorption in the kidney may be enhanced in lieu of increased gluconeogenesis and contributing to the hyperglycemia associated with the development of T2D.Support or Funding InformationThis research was funded by a doctoral fellowship from UC MEXUS‐CONACYT and an MHIRT Fellowship.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.