Silvana Marisa Montenegro

Spontaneous diabetes in eSS rats

SummaryA spontaneous non-insulin-dependent diabetes in a highly inbred line of rats called eSS has been described. It is characterized by early impaired glucose tolerance worsening with age. Males are far more severely affected than females. These animals also exhibit hypertriglyceridemia and hypercholesterolemia. In spite of their hyperglycemia, eSS males have an excess of circulating plasma insulin compared with α controls. Eight-month-old eSS males were sensitive to exogenous insulin. Moreover, as the plasma insulin values decrease with age, glucose tolerance is further impaired. An improvement in the metabolic disturbances was registered in diabetic eSS males under long-term food deprivation. Histopathological examination of the pancreas revealed marked changes compared with age-matched controls. The pancreatic islet structure looked disrupted and islets became smaller and more scattered with advancing age. A diffuse glomerulosclerosis, interstitial lymphocyte infiltrates and tubular nephrosis were present in kidneys.

Hepatic Δ9, Δ6, and Δ5 desaturations in non-insulin-dependent diabetes mellitus eSS rats

Both diabetes mellitus type 1 and diabetes mellitus type 2 are widespread diseases that alter carbohydrate and lipid metabolism. e Stilmann-Salgado (eSS) rats are experimental animals that spontaneously evolve to a state similar to that of young people affected by non-insulin-dependent diabetes mellitus (NIDDM; type 2). Using 6-mon-old eSS rats that, according to the literature [Martinez, S.M., Tarrés, M.C., Montenegro, S, Milo, R., Picena, J.C., Figueroa, N., and Rabasa, S.R. (1988) Spontaneous Diabetes in eSS Rats, Acta Diabetol. Lat. 25, 303–313], had already developed insulin resistance, we investigated the changes evoked on Δ9, Δ6, and Δ5 liver desaturases. The abundance of mRNA and enzymatic activities were measured, as well as the FA composition of liver microsomal lipids. Compared to control rats, the mRNA content and activity of SCD-1 (stearoyl CoA-desaturase, isoform of the Δ9 desaturase) were significantly higher, urase, isoform of the Δ9 desaturase) were significantly higher, whereas the mRNA and activities of Δ6 and Δ5 desaturases were not significantly modified. Correspondingly, the proportion of 18∶1n−9 and the ratios of 18∶1n−9/18∶0 and 16∶1/16∶0 in lipids were significantly increased, whereas the proportion of 20∶4n−6 was unaltered. These effects were found while glycemia was constant or increased. The results are completely opposite those described in insulin-dependent diabetes mellitus (type 1), in which a depression of all the desaturases is found. They suggest that in eSS rats, the activities of the desaturases were not modified by an insulin-resistance effect. Moreover, we suggest that the enhancement of SCD-1 activity might be considered as another typical sign of the NIDDM syndrome, because it has also been found in other animal models of NIDDM, for example, the ones evoked by the sucrose-rich diet and in the Zucker rat.

Intermittent dietary restriction in eSS diabetic rats. Effects on metabolic control and skin morphology

SummaryeSS rats exhibit a non-insulin-dependent diabetic syndrome, significantly influenced by diet. Long-term effects of intermittent dietary restriction were studied in male eSS rats. Experimental animals were fedad libitum during 48h and food-deprived the next 24h (R) while controls (L) of the same strain were freely fed every day. This schedule was maintained from 21 days of age until all rats were sacrificed. R animals were leaner than L rats at 5, 8 and 13 months of age. Moreover, an improved metabolic profile (i.e., lower levels in blood triglycerides, total blood cholesterol, basal blood glucose and blood glucose after an oral glucose load) was found. Histological examination of nuchal skin specimens showed a significant increase of dermal thickness and epidermal hypotrophy in free-fed animals. Collagenous fibers closely packed were found just beneath the dermo-epidermal junction in L rats. This finding was less pronounced in R rats. The above mentioned results suggest that eSS rats would draw advantage from living in environments where food availability is uncertain. The importance of early dietary restrictions in predisposed genotypes appears to be a valuable preventive measure against diabetic evolution and complications.

The eSS rat, a nonobese model of disordered glucose and lipid metabolism and fatty liver

BackgroundeSS is a rat model of type 2 diabetes characterized by fasting hyperglycemia, glucose intolerance, hyperinsulinemia and early hypertriglyceridemia. Diabetic symptoms worsen during the second year of life as insulin release decreases. In 12-month-old males a diffuse hepatic steatosis was detected. We report the disturbances of lipid metabolism of the model with regard to the diabetic syndrome.MethodsThe study was conducted in eight 12-month-old eSS male rats and seven age/weight matched eumetabolic Wistar rats fed with a complete commercial diet al libitum. Fasting plasmatic glucose, insulin, triglycerides, total cholesterol, low-density and high-density lipoprotein, and nonesterified fatty acids levels were measured. Very low density and intermediate-density lipoproteins were analyzed and hepatic lipase activity was determined.ResultseSS rats developed hyperglycemia and hyperinsulinemia, indicating insulin resistance. Compared with controls, diabetic rats exhibited high plasmatic levels of NEFA, triglycerides (TG), total cholesterol (Chol) and LDL-Chol while high-density lipoprotein (HDL) cholesterol values were reduced. eSS rats also displayed TG-rich VLDL and IDL particles without changes in hepatic lipase activity.ConclusionThe nonobese eSS rats develop a syndrome characterized by glucose and lipid disorders and hepatic steatosis that may provide new opportunities for studying the pathogenesis of human type 2 diabetes.

Onset and evolution of nephropathy in rats with spontaneous diabetes mellitus

The occurrence of renal diabetic complications was studied in diabetic nonobese IIM/FmeSS (eSS) rats. The results were compared with eumetabolic Wistar rats paired by sex and age. Between 6 and 12 months of age, eSS male rats had higher fructosamine values and glucose intolerance as well as increasing proteinuria and uremia. Enhancement in water, calcium and phosphorus fractional excretion with a concomitant lower sodium excretion, was observed from 12 months of age on. 18- and 21-month-old eSS rats exhibited fasting hyperglycaemia and rising values of fructosamine, glucose intolerance and glycosuria. Simultaneously, a notorious worsening of proteinuria as well as alterations in glomerular filtration were verified. Optic microscopy of 12-month-old eSS rat kidneys showed areas of tubular dilatation with protein cylinders. In 21-month-old eSS animals, kidneys appeared overtly damaged. Increased capsular, glomerular and Henle’s thin loop diameters were verified in 12-and 21-month-old eSS rats. Glomeruli showed diffuse hypertrophy of mesangial tissue and thickening of the basement membrane. Areas of markedly atrophic and dilated tubules containing acidophilic proteinaceous material were observed. At age of 21 months, kidneys of eumetabolic Wistar control rats presented foci of interstitial and pielic inflammatory infiltrates.ResumenSe investiga la aparición de complicaciones renales en machos de la línea de ratas diabéticas eSS desde los 6 a los 21 meses de edad. Los resultados se comparan con testigos eumetabólicos Wistar. Entre los 6 y 12 meses de edad, los machos eSS presentan intolerancia a la glucosa, elevación de la fructosamina sérica, proteinuria y uremia. También se comprueban aumentos en la excreción fraccional de agua, calcio y fósforo junto con retención en la eliminación de sodio. Durante el segundo año de vida, las ratas eSS evidencian hiperglucemia en situación de ayuno, empeoramiento de la intolerancia glucídica y mayores valores de fructosamina y glucosuria. Simultáneamente, se observa notable aumento de la proteinuria y alteraciones en la filtración glomerular. Con microscopía óptica, los riñones de las ratas eSS de un año presentan áreas de dilatación tubular y cilindros proteicos. Entre los 12 y 21 meses se observa incremento en los diámetros capsular, glomerular y del asa de Henle. A los 21 meses, las ratas eSS muestran glomérulos con engrosamiento del tejido mesangial y de la membrana basal de la cápsula de Bowman, así como áreas de atrofia y dilatación tubular.

A Diachronic Study of Diabetic Nephropathy in Two Autochthonous Lines of Rats to Understand Diabetic Chronic Complications

The worldwide epidemic of Type 2 Diabetes Mellitus, a result of recent deep changes in human lifestyle like sedentary and overly rich nutrition, has dramatic consequences in terms of morbidity, mortality and health care costs (Zimmet et al., 2001). Type 2 Diabetes Mellitus is a complex and multifactorial metabolic disorder which includes distinct nosological entities whose common patterns are hyperglycaemia, resistance to insulin and progressive chronic complications (American Diabetic Association, 2009). A significant proportion of patients will develop a clinically relevant diabetic nephropathy with glomerulopathy, hyalinization of afferent and efferent arterioles, tubular and interstitial lesions (Fioretto et al., 2008). Nephropathy is a very serious complication in both Type 1 and Type 2 Diabetes Mellitus because patients with diabetic kidney disease are at a higher risk of mortality, mostly from cardiovascular complications, than diabetic patients without diabetic nephropathy (Dronavalli & Barkis, 2008). In the Western World the incidence of end-stage renal failure associated to the burden of diabetic nephropathy has increased in recent years and represents a failure of current disease control measure with serious public health implications (Stewart et al, 2006; Villar & Zaoui, 2010). In Latin America, where incidence of Type 2 Diabetes Mellitus is on the rise and has reached epidemic proportions, people usually have poor disease control with the consequence of very high rates of diabetic nephropathy (Caballero & Tenzer, 2007). A study performed in the Asian Pacific region has also shown that diabetic nephropathy was the most common cause of End-Stage Renal Disease in 9 of the 12 countries surveyed and 6 of the 12 countries had greater than 35% of their dialysis patients age 60 years and older (Lee, 2003). In United States, between 20% and 40% of patients ultimately develop diabetic nephropathy, the most common cause of End-Stage Renal Disease requiring dialysis (Dronavalli & Barkis, 2008). Since 2000, the adjusted rate of prevalent End-Stage Renal Disease cases in the United States population ages 65–74, has increased 25 % with an enormous economic impact on the healthcare systems (United States Renal Data System, 2010). In sum, worldwide incidence of diabetic nephropathy, a frequently silent and unrecognized disease, has increased about a 50% between 1998 and 2008 and is now the leading cause of chronic kidney disease and End-Stage Renal Disease (Unites States Renal

Conducta alimentaria y perfil glucémico en dos líneas de ratas con diabetes genética: eSS y eSMT

Introducción. La alimentación puede agravar la diabetes de humanos y modelos animales. Entre ellos, la rata eSMT presenta un curso más exacerbado y mayor biomasa que la línea parental eSS. Objetivo. Estudiar la conducta alimentaria de ratas macho eSMT y eSS ante oferta ilimitada y bajo restricción alternada, analizando su incidencia sobre el peso y la glucemia. Materiales y métodos. Se registró el consumo ad libitum en etapas de crecimiento y mantenimiento. Un grupo de eSMT recibió durante 5 semanas a partir del destete, una dieta restringida intermitente seguida de oferta ilimitada, y otro fue restringido hasta el año de edad, midiéndose el peso y el perfil glucémico en distintas edades. Resultados. Durante el crecimiento, eSMT aumentó de peso más que eSS con ingestas similares, y en la etapa de mantenimiento sustentó mayor biomasa con menor consumo. La restricción intermitente posterior al destete indujo un patrón de crecimiento más lento y menor peso adulto. A los 5 meses presentaron valores de G0 normales (85±12 mg/dl) y los controles mostraron cifras alteradas (119±14 mg/dl). En los animales restringidos la posterior oferta ilimitada produjo glucemias de ayuno compatibles con diabetes (163±25 mg/dl) y un incremento ponderado 75% superior a los alimentados ad libitum. Conclusión. La alternancia prolongada hambre-saciedad indujo en eSMT desaceleración de su metabolopatía mientras que la realimentación se asoció con incrementos superiores de peso y glucemia, atribuibles a un aumento de la eficiencia de conversión inducida por el ayuno. Estos resultados enfatizan la importancia de mejorar el conocimiento sobre las relaciones entre crecimiento, alimentación y diabetes.