Corpulent Rats Research Articles

Can caffeine activate your brown fat? Effects of caffeine, ephedrine, and norepinephrine on nonshivering thermogenesis in congenic lean and obese LA/Ntul//-cp rats

To determine the effects of norepinephrine (NE) or of caffeine (CAF) alone or in combination with ephedrine (EPH) were determined in groups of lean and obese LA/Ntul//-cp Rats, Body weights of obese were >> lean littermates (p=<0.01) and measures of RMR of lean > Obese (p=<0.05). The effects of caffeine, ephedrine, a caffeine+ephedrine combo, and the β- agonist epinephrine was examined. Caffeine (CAF) resulted in a 33% increase in VO2, ‘nonephedrine’ (EPH) a 48% increase, the combination CAF+EPH a 53% increase, and the NE a 33% increase in VO2. In obese rats, the increases in VO2 were of a similar percentage (21 vs 48 vs 47 % vs 31% for CAF, EPH, CAF+EPH and NE respectively although the peak responses attained in the obese tended to be of a significantly lesser absolute magnitude than were observed in the lean phenotype. The time to peak thermogenic response was similar in lean and obese phenotypes for each of the 4 treatment regimens, but the duration of the peak responses to each treatment differed between lean and obese phenotypes (Obese > lean) for CAF, EPH and the CAF+EPH combination but duration of the VO2 response was similar in both phenotypes for the NE treatment. Thus, these observations are consistent with a significant CAF-stimulated thermogenic response that was qualitatively similar to that of NE in both lean and obese phenotypes of the congenic LA/Ntul//-cp rat and which thermogenic responses were further augmented with EPH alone or in combination with CAF. Although the mechanisms of action of the pharmacologic and physiologic mechanisms elicited may differ among the three agents studied the results indicate that they are complimentary in nature in bringing about increases in parameters of nonshivering thermogenesis and thus increasing metabolic energy expenditure in both lean and obese rats. In conclusion, while caffeine as monotherapy may bring about limited weight loss, the combination of caffeine plus ephedrine was more effective in the lean and obese phenotypes of the congenic, non-diabetic LA/Ntul//-cp (Corpulent) rat.

Thermoregulatory dysfunction in post‐weaning congenic corpulent rats

To assess the capacity for cold induced thermoregulation in congenic corpulent rats, groups of normally fed post‐weaning lean and obese LA/Ntul//‐cp rats 6‐9 weeks of age were subjected to a 24°C vs. 4°C environment for < 14 hours. Measures of resting VO2 (RMR) and the thermoregulatory responses to cold exposure, the thermic response to noradrenaline, thyroidal parameters, and measures of core and peripheral body temperatures following cold exposure were obtained. Body weights of obese were greater than in lean rats (p=<0.01), and 14 hours of 4°C exposure demonstrated phenotype effects on both core and rectal temperatures (lean > obese, rectal p=0.0012, core p= 0.0038). The RMR at thermal neutrality and the thermic response to 45 minutes of acute 4°C cold exposure was greater in lean than obese phenotype at all time points measured. The thermic responses to 100 vs 200 µg NE s.c. were greater in lean than in obese rats. Cold exposure induced a significant increase in circulating T3 and the T3:T4 ratios but T4 concentrations were unchanged by cold exposure challenge. Phenotype effects on outer ring T4‐5’ deiodinase activity/mg protein were present in Kidney and Liver (Lean > Obese) while Interscapular brown adipose tissue (IBAT) demonstrated both phenotype and cold induced effects (Obese > Lean). In contrast, T4‐5’deiodinase activity in gastrocnemius muscle tissue was similar in both phenotypes and lacked cold induced effects (p= n.s.). The results of this study indicate that an impaired capacity for thermoregulation occurs early in the lifespan of the corpulent rat, despite a robust increase in total IBAT 5’deiodinase activity and in circulating T3 concentrations following cold exposure in both lean and obese phenotypes. While the physiologic basis for the elevated T3 concentrations following cold exposure remains unclear and are likely secondary to the combined effects of optimizing peripheral T4 to T3 conversion rates in both phenotypes, and possible changes in kinetics of T3 receptor binding and clearance in IBAT and other tissues and which may contribute to a greater caloric efficiency and propensity for weight gain in the obese phenotype.

Differential expression T4‐5’‐deiodinase activity in corpulent rats following cold exposure

Multiple studies indicate that the thermic responses to diet and cold exposure may be impaired in obese rodents and are likely secondary to the combined contributions of sympathetic and thyroidal components of nonshivering thermogenesis (NST). T4 is normally deiodinated via outer ring deiodinase activity by D‐1 and/or D‐2 deiodinase activity to form hormonaly active T3 during fed and cold environments, or inner ring deiodinase activity via D‐3 to form reverse T3 (rT3) during food or energy deprivation. The effect of 14 hours of 4°C cold exposure on the obese phenotype of the LA/Ntul//‐cp rats was determined in normally reared young female animals 8 to 9 weeks of age and fed the Purina Chow #5012 ad libitum throughout. Body weights and adipose tissue mass were greater in the obese than the lean phenotype (p=<0.05). RMR and the dose related thermic responses to norepinephrine (NE, 200 ug., s.c.) were greater in lean than in obese. Cold exposure at 4°C resulted in decreases in rectal but not core temperature in obese rats, and the thermic responses to 45 minutes of 4°C cold exposure on VO2 were typical but were significantly greater in lean than obese animals at all time points measured. Circulating T4 concentrations were similar in lean and obese rats and serum T3 but not T4 concentrations increased dramatically in both phenotypes following the cold exposure, consistent with phenotype‐ and maximal IBAT‐linked changes in T4‐5’‐deiodinase activity / mg protein in kidney, liver and IBAT and in temperature linked increases in IBAT deiodinase activity / mg tissue protein in this strain. When D‐1 and D‐2 deiodinase activity was computed / tissue mass, further analysis indicated that D‐1 was the predominating deiodinase in liver, kidney, and gastrocnemius muscle, while in IBAT D‐2 > D‐1 activity / IBAT depot and was greater in obese than lean rats. Cold exposure was associated with modest increases in net kidney deiodinase activity only in kidney. Thus, the cold induced increases in circulating T3 in lean and obese rats are likely attributed at least in part to modest increases in renal T4‐5’ D‐2 deiodinase activity, in addition to maximal rates of conversion in other tissues in possible combination with decreases in hormone clearance rates during cold induced stress.

Effect of adrenalectomy and insulin resistance on non‐shivering thermogenesis in the corpulent rat

Glucocorticoid hormones have been reported to impede optimal insulin sensitivity and glucose uptake in peripheral tissues via interactions with GLUT transporters, leading to insulin resistance and impaired glucose uptake via GLUT transporters. The LA/Ntul//‐cp rat expresses obesity in 25% of the offspring by 5 to 6 weeks of age but remains non diabetic throughout much if not all of its lifespan when normally reared. Groups of congenic lean and obese LA/Ntul//‐cp rats were fed low glycemic Purina Chow diets from 6 to 9 weeks of age or overfed with a high energy cafeteria diet (Café) from 9 until 12 weeks of age. Subgroups of obese animals were adrenalectomized (ADX) at 6 weeks of age (WoA) and subjected to the same dietary regimen to determine if the Café overfeeding could enhance the normal thermic response to norepinephrine (NE) in the obese phenotype and to determine if ADX would result in a restoration of glycemic status and NE‐induced thermogenesis in the obese phenotype. Measures of Oral Glucose Tolerance (OGT), Area under the glucose curve (AUC), and NE‐stimulated VO2 were determined (NE, 200 µg, s.c.) at 6, 9 and 12 WoA in all treatment groups and Insulin:Glucose ratios (I:G) at 12 WoA. Obese animal demonstrated hyperphagia at all ages studied, and Obese ADX hyperphagia from 9 to 12 WoA. OGT and AUC indicated modest glucose intolerance in the obese phenotype, and which was restored following ADX at 6 and 9 WoA. NE resulted in a progressive increase in VO2 in lean rats at each age studied, but NE‐stimulated VO2 was lower in the obese phenotype and decreased further after the Café feeding regimen. ADX was associated with a restoration of OGT, I:G and NE stimulated VO2 equivalent to that observed in lean animals at 12 weeks of age. These results are consistent with adrenocorticoid‐mediated insulin resistance likely due to a receptor level defect in insulin sensitivity as a contributory factor in the impairment in OGT and NST in the obese phenotype of this strain.

Impaired physiological thermoregulation in postweaning obese female LA/Ntul//-cp (corpulent) rats

Groups of lean and obese female lean, and obese LA/Ntul//cp (corpulent) rats were subjected to measures of thermic responses to feeding, noradrenaline administration, and responses to 14 hours of cold exposure to access their capacity for thermoregulation beginning at 6 to 8 weeks of age. Body weights and adipose tissue mass were greater in the obese than the lean phenotype (p=<0.05). RMR and the dose related thermic responses to norepinephrine (NE) in lean were greater than in obese. Cold exposure at 4°C resulted in decreases in rectal but not core temperature in obese rats, and the thermic responses to 45 minutes of 4°C cold exposure on VO2 were typical but were significantly greater in lean than obese animals at all points measured. Circulating thyroid hormone concentrations were similar in lean and obese rats and T3 but not T4 increased dramatically in both phenotypes following the cold exposure, consistent with phenotype- and IBAT-linked changes in T4-5’ deiodinase and thyroidal activity in this strain. These thermoregulatory changes are consistent with previous studies and may contribute to phenotype mediated aspects of energy metabolism, storage, and adipose tissue deposition and to a phenotype specific selective epigenetic propensity for the expression of obesity during the early postweaning period

Adrenalectomy improves glycemic responses in congenic obese LA/Ntul//-cp RATS

To determine the effects of adrenalectomy on typical insulin-mediated glycemic responses in male obese rats, groups (n=6 -12 rats/phenotype) of normally reared congenic lean and obese animals were fed a Purina chow diet from 6 to 9 weeks of age, and the Chow diet plus a highly palatable cafeteria diet from 9 to 12 weeks of age. The congenic LA/Ntul//-cp rat strain is noted for its longevity and early expression of the obese trait but remains non-diabetic throughout much if not all of its normal lifespan. Subgroups of obese animals were subjected to bilateral adrenalectomy (ADX) at 6 weeks of age to remove glucocorticoid contributions to glycemic parameters. Measures of weight gain (WG )and of glucose tolerance (OGT) were obtained in the three treatment groups at 6, 9 and 12 weeks of age. WG on ADX-obese rats was similar to that of their lean littermates at 6 and 9 weeks of age on the chow diet but increased to twice that observed in their lean littermates from 9 to 12 weeks of age. OGT responses after 30 to 60 minutes and the area under the OGT curve were impaired but not diabetic in obese animals at all ages compared to lean littermates and returned toward those of normally lean rats after ADX. The Insulin to glucose ratio (I:G) was also consistent with insulin resistance in obese but not in ADX-obese or lean rats at 12 weeks of age. In conclusion, ADX resulted in normalization of OGT and glycemic parameters in the obese phenotype at 9 and 12 weeks of age. These results are consistent with normalization of typical insulin-mediated components of glycemic parameters and glucose uptake in peripheral tissues following adrenalectomy of congenic obese rats. The results further suggest that the counterregulatory effects of insulin and glucocorticoid hormones may be contributory to the impaired glycemic responses in the obese phenotype of the LA/N//-cp (corpulent) rat and are consistent with a receptor-mediated element in the development of insulin resistance and glucose uptake in peripheral tissues commonly associated with the early development of obesity in this strain.

Effect of adrenalectomy and glycemic status on caloric efficiency and adiposity in the congenic LA/Ntul//-cp (corpulent) rat

Obesity develops in the obese phenotype of the congenic LA/Ntul//-cp (corpulent) rat strain by 6 weeks of age.1 To gain insight into the contributors to the expression of obesity in the obese phenotype of this strain, groups [n=12-20 rats/phenotype] of congenic male lean and obese LA/Ntul//-cp (corpulent) rats were fed an ad libitum standardized Purina chow diet (CHOW) from 6 to 12 weeks or age, and subgroups (n=6 rats / subgroup) were overfed with a highly palatable cafeteria diet (CAFÉ) from 9 to 12 weeks of age (WOA). A subgroup of obese rats (n=6) were subjected to bilateral adrenalectomy (ADX) at 6 WOA and followed the same dietary regimen and treatment schedule. BW of lean and obese animals were similar at 6 WOA and increased by 88% in lean phenotype and 281% in obese phenotype during the 6 weeks study, while in ADX obese rats, BW were similar at 6 and 9 WOA but BW increased to 2.5-fold above starting weights and 1.8-fold above 9-week weights between 9 and 12 WOA. The CAFE supplement was without significant effect on final body weights in the lean phenotypes, but was associated with significantly greater body weights at ages 9 and 12 WOA in the obese phenotype (p=<0.05) and in the obese-ADX at 12 WOA. CE (kcal/gram gain of BW per day) remained relatively constant in lean and obese-ADX rats throughout the study, but CE was more efficient in the obese phenotype at all ages studied and was more efficient with the CAFE supplement feeding regimen. Fasting I:G ratios at 12 weeks of age were 4.2-fold greater in obese than lean and were partially normalized in obese-ADX to 1.7-fold increase at 12 WOA. Relative adiposity of obese rats was 3.8-fold greater in obese than lean phenotype, with the greatest increase in the SQ depot. Resting VO2 (RMR) was lower in obese than lean rats at each age studied and was increased by ADX. Thermogenic interscapular brown adipose tissue (IBAT) mass was greater in obese and obese-ADX than lean rats. The results of this study indicate that CE is associated with the predisposition for the expression and development of adiposity in the obese phenotype of this strain and is associated with an increased I:G ratio and IBAT mass that is consistent with insulin resistance and an impaired capacity for energy expenditure and became normalized on the Chow but not the CAFE diet following ADX. These observations implicate likely multiple metabolic factors that contribute to a greater efficiency of energy storage, utilization and or energy conservation in the obese than in the lean phenotype of this strain and which is partially corrected in the obese phenotype by ADX. The metabolic impact of added caloric intake was associated with an additive impact on the CE of weight gain and adiposity in the obese phenotype of this congenic rodent strain and was partially corrected via ADX

Residual thermic effects of diet induced thermogenesis (RDIT) in aging lean and obese LA/Ntu1//-cp (corpulent) rats

Diet induced thermogenesis has been proposed to account for up to 15% of the caloric content of an ingested meal and to become decreased with aging and in obesity. Genetically obese rodents have been shown to exhibit impairments in the thermic responses to diet and environment, which may partially account for an improved caloric efficiency and to contribute to their increased propensity to become obese. In the present study we sought to determine the thermic responses to diet and environment in aging obese rats when young, middle aged, and aged. Resting oxygen consumption tended to decrease with advancing age and the thermic responses were lower than predicted in obese than in lean rats. This study provides important new insights regarding the thermogenic effects of diet and diet induced thermogenesis and their potential contributions to mechanisms of energy balance across the spectrum of aging in lean and obese LA/Ntul//-cp rats

Decreased Capacity for Thermogenesis During Aging in Lean and Obese LA/Ntul//‐ cp (corpulent) Rats

Obesity develops in the obese phenotype of the LA/Ntul//-cp (corpulent) rat strain by 6 weeks of age. Groups [n=12-20 rats/phenotype] of congenic female lean and obese LA/Ntul//-cp (corpulent) rats were fed ad libitum standardized Purina #5012 diet for 4, 14, or 24 months of age. Measures of Body weight (BW) and of resting metabolic rate (RMR) at thermal neutrality, and for up to 45 minutes of 4°C spontaneous cold exposure, and norepinephrine-stimulated (NE) thermogenesis (100 µg sc) were determined at each age. BW of lean rats increased only gradually during the study (p=N.S.), but BW of obese phenotype were 2-fold greater at 4 months (p=0.05) and increased progressively to 4-fold greater than lean littermates by 24 months of age (p=<0.01). RMR in the lean phenotype decreased gradually at each age (p=<0.05) and was greater in the lean than the obese phenotype at all ages studied (p=<0.05). Cold exposure resulted in a dramatic 5-fold increase in the VO2 after 5 minutes in 4-month-old rats, which increase in thermogenesis was less dramatic at each successive age. In 24-month-old lean rats however, the cold induced increases in RMR were markedly diminished to only ~3x RMR at 5 minutes cold exposure but remained similar to the other lean age groups thereafter. In the obese phenotype, the peak responses at 5 minutes were significantly lower than those of lean rats at 5 minutes in 4- and 14-month-old rats and were also markedly impaired in 24-month-old obese rats. NE resulted in a 1.5-fold increase in VO2 in the lean phenotype at all ages studied, while in obese rats NE resulted in a ~1.4-fold increase in VO2 at 4 months with non-significant 1.2-fold increases at the two older ages. In both phenotypes, the RMR and the NE-stimulated VO2 responses tended to decrease with increasing age. The results of this study demonstrate that the body weights of the obese phenotype are significantly greater than their lean littermates throughout the age spectrum studied from 6 weeks of age, and that both resting RMR, cold, and NE-stimulated thermogenesis are decreased in the obese compared to the lean phenotype, become further decreased with advancing age, and may be a contributing factor in the efficiency of energy conservation and expenditure in the obese phenotype of this animal strain.

Enhanced Caloric Efficiency Contributes to Adiposity in LA/N//‐ cp Corpulent Rats

Obesity is readily detected among 25% of the offspring of the congenic LA/Ntul//-cp (corpulent) rat strain by 5 to 6 weeks of age where it occurs as an autosomal recessive trait. The obese phenotype of this strain demonstrates characteristic glucose intolerance and varying degrees of insulin resistance, but typically remains euglycemic following insulinogenic dietary regimens. Groups [n=12-20 rats/phenotype] of female congenic lean and obese LA/Ntul//-cp rats were ad libitum fed standardized Purina #5012 stock diets for 4, 14, or 24 months or the same diet plus a 16% (w/v) sucrose solution (SSOL) supplement from 12 weeks of age, and measures of body weight (BW), caloric intake (CI), and caloric efficiency (CE) determined as outlined by Vedula et al at each age studied. BW of lean animals remained similar at all ages, while BW of obese phenotype were significantly greater than their lean littermates at each age studied. The SSOL supplement was without significant effect on final BW in the lean phenotypes at all ages studied (p=n.s.) but were associated with greater BW at ages 14 and 24 months of age in the obese phenotype (p=<0.05). CE was determined as the ratio of kcal/gram of BW per day remained relatively constant in lean animals throughout the age range, but CE was more efficient in the obese phenotype at all ages studied and became progressively more efficient with the SSOL supplement feeding with increasing age. The results of this study indicate that CE is associated with the predisposition for the development of obesity in the obese phenotype of this strain and likely implicates multiple metabolic factors that contribute to a greater efficiency of energy utilization and or energy conservation in the obese than in the lean phenotype of this strain, and the metabolic impact of added sucrose as a SSOL was associated with an additive impact on the CE of weight gain and adiposity in the obese phenotype of this congenic rodent strain. The implications of the greater adiposity and CE among the obese phenotype when ingesting the insulinogenic SSOL supplement being associated with increasing degrees of insulin resistance is a new finding for this strain of obese rodent and will be discussed. References 1Hansen, CT. The development of the SHR/N- and LA/N-cp Congenic Rat Strains. NIH pub, Div of Res Serv, Vet Res Br, NIH, Bethesda, MD p. 7-10. 1988 2Tulp, OL. Characteristics of thermogenesis, obesity, and longevity in the LA/N–cp rat. ILAR News 32(3), 32-39, 1990. 3Vedula, U, Schnitzer-Polokoff, R and Tulp. OL. The effect of acarbose on the food intake, weight gain, and adiposity of LA/N-cp rats. Comp. Biochem. Physiol. A Comp. Physiol., 100. pp. 477-482, 1991. 4Tulp, O.L. and Brown T. Effect of a Fructan-Chromium Complex on Glycemic Responses of Congenic Obese LA/Ntul/ /-cp Rats. Adv in Obes, Weight Mgmt & Control, 2016. 5Michaelis, OE. IV, Ellwood, KC, Tulp, OL and Greenwood, MRC. Effect of feeding sucrose or starch diets on parameters of glucose tolerance in the LA/N-cp rat. Nutr. Res., 6(2): 95-99, 1986. 6Bukowiecki LJ, Deshaies, Y, Collet, AJ and Tulp, O. “Major thermogenic defect associated with insulin resistance in brown adipose tissue of obese-diabetic SHR/N–cp rats”, Am J Physiol 261 (Endo Metab) E204-213, 1991.

Thermogenesis, aging and obesity in the LA Ntul/-cp (corpulent) rat

Obesity and mild to moderate impaired carbohydrate tolerance develops in the obese phenotype of the LA/Ntul//-cp (corpulent) rat strain by 6 weeks of age. Groups (n=12-20 rats/phenotype] of female congenic lean and obese LA/Ntul//-cp (corpulent) rats were fed ad libitum standardized Purina #5012 diet ad house water for 4, 14, or 24 months of age. Measures of Body weight (BW) and of resting oxygen consumption (RMR; VO2) at thermal neutrality and for up to 45 minutes of (4°C) spontaneous cold exposure, and norepinephrine-stimulated thermogenesis (100 ug. s.c.) were determined at each age. Body weights of lean rats increased only gradually during the study (p=n.s.), but weights of obese phenotype were ~2-fold greater at 4 months (p=&lt;0.05), 14 months (p-&lt;0.01), and ~3.5 to 4-fold greater at 24 months of age (p=&lt;0.01). Resting metabolic rates in the lean phenotype trended to decrease modestly by 24 months (p=&lt;0.05) and were greater than resting metabolic rates in the obese phenotype at all ages studied (p=&lt;0.05). Cold exposure at 4°C resulted in a dramatic ~5-fold increase in the oxygen consumption after 5 minutes in 4-month-old rats, which subsided to ~2x resting metabolic rate within 15 minutes and remained constant thereafter in the lean phenotype. In 14-months old lean rats the increase in oxygen consumption at 5 minutes averaged ~4-fold increase over resting levels and returned to ~2x resting levels from 15 to 45 minutes 4°C exposure. In 24-month-old lean rats however, the cold induced increases in metabolism were markedly diminished to only ~3x resting metabolic rates at 5 minutes cold exposure but remained similar to the other lean age groups thereafter. In the obese phenotype, the peak responses at 5 minutes were lower than those of lean rats at 5 minutes in 4- and 14-month-old rats and were significantly impaired in 24-month-old rats at all times measured. Norepinephrine resulted in a &gt;1.5-fold increase in oxygen consumption in the lean phenotype at all ages studied, while in obese rats norepinephrine resulted in a~1.4-fold increase in oxygen consumption at 4 months of age with non-significant ~1.1 to 1.2-fold increases at the two older ages. In both phenotypes, the resting and the norepinephrine-stimulated oxygen consumption responses tended to decrease with increasing age. The results of this study demonstrate that the body weights of the obese phenotype are significantly greater than their lean littermates throughout the age spectrum studied, and that both resting metabolic rates, 4°C cold, and norepinephrine-stimulated thermogenesis are decreased in the obese compared to the lean phenotype and become further decreased with advancing age

Effects of aging, phenotype and carbohydrate feeding on caloric efficiency and adiposity in the LA/Ntul//-cp (corpulent) rat

Obesity develops in the obese phenotype of the LA/Ntul//-cp (corpulent) specific pathogen-free rat strain by 5 to 6 weeks of age. Groups [n=12 -20 rats/phenotype] of female congenic lean and obese LA/Ntul//-cp (corpulent) rats were fed ad libitum standardized Purina diets for 4, 14, or 24 months or the same diet plus a 16% (w/v) sucrose solution supplement from 12 weeks of age, and measures of body weight, caloric intake, and caloric efficiency (CE) determined at each age group. Body weights of lean animals remained similar at all ages studied, while body weights of obese phenotype were significantly greater than their lean littermates at each age studied. The sucrose supplement was without significant effect on final body weights in the lean phenotypes at all ages studied (p=n.s.) but were associated with greater body weights at ages 4, 14 and 24 months of age in the obese phenotype (p=&lt;0.05). CE was determined as the ratio of kcal/gram of body weight per day remained relatively constant in lean animals throughout the age range, but CE was more efficient in the obese phenotype at all ages studied and became progressively more efficient with the sucrose supplement feeding with increasing age. The results of this study indicate that CE is associated with the predisposition for the development of obesity in the obese phenotype of this strain and likely implicates multiple metabolic factors that contribute to a greater efficiency of energy utilization and or energy conservation in the obese than in the lean phenotype of this strain, and the metabolic impact of added sucrose was associated with an additive impact on the CE of weight gain and adiposity in the obese phenotype of this congenic rodent strain

Influence of metabolic syndrome on post-stroke outcome, angiogenesis and vascular function in old rats determined by dynamic contrast enhanced MRI

Stroke affects primarily aged and co-morbid people, aspects not properly considered to date. Since angiogenesis/vasculogenesis are key processes for stroke recovery, we purposed to determine how different co-morbidities affect the outcome and angiogenesis/vasculogenesis, using a rodent model of metabolic syndrome, and by dynamic enhanced-contrast imaging (DCE-MRI) to assess its non-invasive potential to determine these processes. Twenty/twenty-two month-old corpulent (JCR:LA-Cp/Cp), a model of metabolic syndrome and lean rats were used. After inducing the experimental ischemia by transient MCAO, angiogenesis was analyzed by histology, vasculogenesis by determination of endothelial progenitor cells in peripheral blood by flow cytometry and evaluating their pro-angiogenic properties in culture and the vascular function by DCE-MRI at 3, 7 and 28 days after tMCAO. Our results show an increased infarct volume, BBB damage and an impaired outcome in corpulent rats compared with their lean counterparts. Corpulent rats also displayed worse post-stroke angiogenesis/vasculogenesis, outcome that translated in an impaired vascular function determined by DCE-MRI. These data confirm that outcome and angiogenesis/vasculogenesis induced by stroke in old rats are negatively affected by the co-morbidities present in the corpulent genotype and also that DCE-MRI might be a technique useful for the non-invasive evaluation of vascular function and angiogenesis processes.

Reparative effects of interleukin-1 receptor antagonist in young and aged/co-morbid rodents after cerebral ischemia

Neuroprotective strategies for ischemic stroke have failed to translate from bench to bedside, possibly due to the lack of consideration of key clinical co-morbidities. Stroke and co-morbidities are associated with raised levels of the pro-inflammatory cytokine interleukin-1 (IL-1). Inhibition of IL-1 by the administration of interleukin-1 receptor antagonist (IL-1Ra) has shown to be neuroprotective after experimental cerebral ischemia. Stroke can also trigger a robust neuroreparative response following injury, yet many of these new born neurons fail to survive or integrate into pre-existing circuits. Thus, we explore here effects of IL-1Ra on post-stroke neurogenesis in young and aged/co-morbid rats. Aged lean, aged Corpulent (a model of atherosclerosis, obesity and insulin resistance) and young Wistar male rats were exposed to transient cerebral ischemia, received subcutaneous IL-1Ra 3 and 6h during reperfusion, and effects on stroke outcome and neurogenesis were analyzed. Our results show that administration of IL-1Ra improves stroke outcome in both young and aged/co-morbid rats. Furthermore, IL-1Ra not only increases stem cell proliferation, but also significantly enhances neuroblast migration and the number of newly born neurons after cerebral ischemia. Overall, our data demonstrate that systemic administration of IL-1Ra improves outcome and promotes neurogenesis after experimental stroke, further highlighting the therapeutic potential of this clinically approved drug.

Cardiomyocyte Antihypertrophic Effect of Adipose Tissue Conditioned Medium from Rats and Its Abrogation by Obesity is Mediated by the Leptin to Adiponectin Ratio.

White adipocytes are known to function as endocrine organs by secreting a plethora of bioactive adipokines which can regulate cardiac function including the development of hypertrophy. We determined whether adipose tissue conditioned medium (ATCM) generated from the epididymal regions of normal rats can affect the hypertrophic response of cultured rat ventricular myocytes to endothelin-1 (ET-1) administration. Myocytes were treated with ET-1 (10 nM) for 24 hours in the absence or presence of increasing ATCM concentrations. ATCM supressed the hypertrophic response to ET-1 in a concentration-dependent manner, an effect enhanced by the leptin receptor antagonist and attenuated by an antibody against the adiponectin AdipoR1 receptor. Antihypertrophic effects were also observed with ATCM generated from perirenal-derived adipose tissue. However, this effect was absent in ATCM from adipose tissue harvested from corpulent JCR:LA-cp rats. Detailed analyses of adipokine content in ATCM from normal and corpulent rats revealed no differences in the majority of products assayed, although a significant increase in leptin concentrations concomitant with decreased adiponectin levels was observed, resulting in a 11 fold increase in the leptin to adiponectin ratio in ATCM from JCR:LA-cp. The antihypertrophic effect of ATCM was associated with increased phosphorylation of AMP-activated protein kinase (AMPK), an effect abrogated by the AdipoR1 antibody. Moreover, the antihypertrophic effect of ATCM was mimicked by an AMPK activator. There was no effect of ET-1 on mitogen-activated protein kinase (MAPK) activities 24 hour after its addition either in the presence or absence of ATCM. Our study suggests that adipose tissue from healthy subjects exerts antihypertrophic effects via an adiponectin–dependent pathway which is impaired in obesity, most likely due to adipocyte remodelling resulting in enhanced leptin and reduced adiponectin levels.

Expression of proteins associated with adipocyte lipolysis was significantly changed in the adipose tissues of the obese spontaneously hypertensive/NDmcr-cp rat

BackgroundThe etiology of the metabolic syndrome is complex, and is determined by the interplay of both genetic and environmental factors. The present study was designed to identify genes and proteins in the adipose tissues with altered expression in the spontaneously hypertensive/NIH –corpulent rat, SHR/NDmcr-cp (CP) and to find possible molecular targets associated with the pathogenesis or progression of obesity related to the metabolic syndrome.MethodsWe extracted RNAs and proteins from the epididymal adipose tissues in CP, SHR/Lean (Lean), and Wistar Kyoto (WKY) rats and performed microarray analysis and two-dimensional difference in gel electrophoresis (2D-DIGE) linked to a matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS).ResultsThe results showed different mRNA and protein expression levels in the adipose tissue: oligo DNA microarray identified 33 genes that were significantly (P < 0.01) up-regulated and 17 genes significantly down-regulated in CP compared with WKY and Lean rats at both 6 and 25 weeks of age. The affected genes-proteins were associated with lipolytic enzymes stimulated by peroxisome proliferator-activated receptor (PPAR) signaling. Further analysis using the 2D-DIGE connected with MALDI-TOF/TOF analysis, the expression of monoglyceride lipase (MGLL) was significantly up-regulated and that of carboxylesterase 3 (CES3) was significantly down-regulated in 6- and 25-week-old CP compared with age-matched control (WKY and Lean rats).ConclusionsOur results suggest the possible involvement of proteins associated with adipocyte lipolysis in obesity related to the metabolic syndrome.

Altered gene and protein expression in liver of the obese spontaneously hypertensive/NDmcr-cp rat

BackgroundIt is difficult to study the mechanisms of the metabolic syndrome in humans due to the heterogeneous genetic background and lifestyle. The present study investigated changes in the gene and protein profiles in an animal model of the metabolic syndrome to identify the molecular targets associated with the pathogenesis and progression of obesity related to the metabolic syndrome.MethodsWe extracted mRNAs and proteins from the liver tissues of 6- and 25-week-old spontaneously hypertensive/NIH –corpulent rat SHR/NDmcr-cp (CP), SHR/Lean (Lean) and Wistar Kyoto rats (WKY) and performed microarray analysis and two-dimensional difference in gel electrophoresis (2D-DIGE) linked to a matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS).ResultsThe microarray analysis identified 25 significantly up-regulated genes (P < 0.01; log10 > 1) and 31 significantly down-regulated genes (P < 0.01; log10 < −1) in 6- and 25-week-old CP compared with WKY and Lean. Several of these genes are known to be involved in important biological processes such as electron transporter activity, electron transport, lipid metabolism, ion transport, transferase, and ion channel activity. MALDI-TOF/TOF MS identified 31 proteins with ±1.2 fold change (P < 0.05) in 6- and 25-week-old CP, compared with age-matched WKY and Lean. The up-regulated proteins are involved in metabolic processes, biological regulation, catalytic activity, and binding, while the down-regulated proteins are involved in endoplasmic reticulum stress-related unfolded protein response.ConclusionGenes with significant changes in their expression in transcriptomic analysis matched very few of the proteins identified in proteomics analysis. However, annotated functional classifications might provide an important reference resource to understand the pathogenesis of obesity associated with the metabolic syndrome.

Delayed Administration of Interleukin-1 Receptor Antagonist Reduces Ischemic Brain Damage and Inflammation in Comorbid Rats

Many neuroprotective agents have been effective in experimental stroke, yet few have translated into clinical application. One reason for this may be failure to consider clinical comorbidities/risk factors in experimental models. We have shown that a naturally occurring interleukin-1 receptor antagonist (IL-1Ra) is protective against ischemic brain damage in healthy animals. However, protective effects of IL-1Ra have not been determined in comorbid animals. Thus, we tested whether IL-1Ra protects against brain injury induced by experimental ischemia in aged JCR-LA (corpulent) rats, which have clinically relevant risk factors. Male, aged, lean, and corpulent rats exposed to transient (90 minutes) occlusion of the middle cerebral artery (tMCAO) were administered two doses of IL-1Ra (25 mg/kg, subcutaneously) during reperfusion. Brain injury and neuroinflammatory changes were assessed 24 hours after tMCAO. Our results show that IL-1Ra administered at reperfusion significantly reduced infarct volume measured by magnetic resonance imaging (50%, primary outcome) and blood-brain barrier disruption in these comorbid animals. Interleukin-1Ra also reduced microglial activation, neutrophil infiltration, and cytokines levels in the brain. These data are the first to indicate that IL-1Ra protects against ischemic brain injury when administered via a clinically relevant route and time window in animals with multiple risk factors for stroke.

Differential effects of inhalation exposure to PM2.5 on hypothalamic monoamines and corticotrophin releasing hormone in lean and obese rats

Acute exposure to airborne pollutants, especially particulate matter (PM2.5) is known to increase hospital admissions for cardiovascular conditions, increase cardiovascular related mortality and predispose the elderly and obese individuals to cardiovascular conditions. The mechanisms by which PM2.5 exposure affects the cardiovascular system is not clear. Since the autonomic system plays an important role in cardiovascular regulation, we hypothesized that PM2.5 exposure most likely activates the paraventricular nucleus (PVN) of the hypothalamus to cause an increase in sympathetic nervous system and/or stress axis activity. We also hypothesized that these changes may be sustained in obese rats predisposing them to higher cardiovascular risk. To test this, adult male Brown Norway (BN) rats were subjected to one day or three days of inhalation exposures to filtered air (FA) or concentrated air particulate (CAP) derived from ambient PM2.5. Corpulent JCR-LA rats were exposed to FA or CAP for four days. Animals were sacrificed 24h after the last inhalation exposure. Their brains were removed, frozen and sectioned. The PVN and median eminence (ME) were microdissected. PVN was analyzed for norepinephrine (NE), dopamine (DA) and 5-hydroxy-indole acetic acid (5-HIAA) levels using HPLC-EC. ME was analyzed for corticotrophin releasing hormone (CRH) levels by ELISA. One day exposure to CAP increased NE levels in the PVN and CRH levels in the ME of BN rats. Repeated exposures to CAP did not affect NE levels in the PVN of BN rats, but increased NE levels in JCR/LA rats. A similar pattern was observed with 5-HIAA levels. DA levels on the other hand, were unaffected in both BN and JCR/LA strains. These data suggest that repeated exposures to PM2.5 continue to stimulate the PVN in obese animals but not lean rats.

Relationship of glucose and oleate metabolism to cardiac function in lipin-1 deficient (fld) mice

Lipin-1 is the major phosphatidate phosphatase (PAP) in the heart and a transcriptional coactivator that regulates fatty acid (FA) oxidation in the liver. As the control of FA metabolism is essential for maintaining cardiac function, we investigated whether lipin-1 deficiency affects cardiac metabolism and performance. Cardiac PAP activity in lipin-1 deficient [fatty liver dystrophy (fld)] mice was decreased by >80% compared with controls. Surprisingly, oleate oxidation and incorporation in triacylglycerol (TG), as well as glucose oxidation, were not significantly different in perfused working fld hearts. Despite this, [³H]oleate accumulation in phosphatidate and phosphatidylinositol was increased in fld hearts, reflecting the decreased PAP activity. Phosphatidate accumulation was linked to increased cardiac mammalian target of rapamycin complex 1 (mTORC1) signaling and endoplasmic reticulum (ER) stress. Transthoracic echocardiography showed decreased cardiac function in fld mice; however, cardiac dysfunction was not observed in ex vivo perfused working fld hearts. This showed that changes in systemic factors due to the global absence of lipin-1 could contribute to the decreased cardiac function in vivo. Collectively, this study shows that fld hearts exhibit unchanged oleate esterification, as well as oleate and glucose oxidation, despite the absence of lipin-1. However, lipin-1 deficiency increases the accumulation of newly synthesized phosphatidate and induces aberrant cell signaling.