Page 69 - GTM-4-2

Global Translational Medicine Glucosidase and metabolic profiles

through the expression of an autosomal recessive trait, to be linked to a genetic predisposition, independent of
and are soon accompanied by the commonly observed dietary or environmental factors.
progression of chronic pathophysiologic sequelae,
including abnormalities in plasma cholesterol levels and 2. Materials and methods
lipid profiles. Preliminary observations suggest that the Two groups of congenic obese male SHR/Ntul//-cp rats

development of hyperglycemia and hyperinsulinemia in (n=8 rats/group) were housed under standard laboratory
T2DM is less severe in females than in males. F1 hybrids conditions, including a temperature of 21 – 22°C, 50%
with the non-diabetic LA/Ntul//-cp strain exhibit what relative humidity, and a reverse light cycle (darkness from
appears to be a genetic dilution of obesity-linked T2DM, 0800 to 2000 daily) in adjacent hanging steel cages with
although the obese phenotype remains. Thus, the T2DM individual occupancy. The animals were fed Purina Chow
in this strain occurs reproducibly with normal, otherwise and provided with house water ad libitum from weaning to
healthful diets, in contrast to high-fat diets or other dietary 8 weeks of age, at which point early stages of obesity and
extremes used to induce diabetic symptoms, as has been T2DM were clearly established, with glycosuria and T2DM
employed in other strains of obese rodents, resembling the confirmed. It is noteworthy that, in this animal model,
inheritance patterns of obesity and T2DM in humans. 17-26 the onset of obesity and T2DM occurs spontaneously

The congenic spontaneously hypertensive and diabetes- soon after weaning due to a genetic predisposition, likely
prone (SHR)/Ntul//-cp rat model was developed in the resulting from a Tyr763Stop mutation in the extracellular
small animal genetics unit by Hansen at the National domain of the leptin receptor, and is independent of
26
Institutes of Health (NIH) by incorporating the -cp trait specific dietary or environmental interactions. Thus, the
from the Koletsky rat into a longevity-prone NIH (N) strain specific metabolic pathways involved in the progression
of unknown origin. This step was followed by crossing the to the metabolic sequelae of obesity and T2DM are
20
N-cp (NIH) strain with the SHR rat, with 12 or more cycles currently unclear, beyond their genomic origin. All rats
of backcrossing. This level of backcrossing was deemed demonstrated glycosuria, confirmed by test strips, by
sufficient to establish a congenic status, ensuring that 8 weeks of age, which persisted thereafter (Urine Glucose
99.9% or more of the original genome remained authentic Test Strips, OneStep). At 8 weeks of age, the rats were
while preserving the SHR and -cp traits. In this model, all switched to a semi-purified control diet developed by the
offspring are deemed genetically identical, and 25% of the Carbohydrate Nutrition Laboratories of the United States
20
offspring of breeding pairs heterogenous for the -cp trait Department of Agriculture. This diet contained 54%
will inherit the trait. The hypertensive trait is preserved carbohydrate as sucrose, 20% protein (equal parts casein
only in the lean phenotype, while T2DM develops soon and lactalbumin), 5.9 % cellulose, 16% fat (equal parts beef
after weaning as a recessive trait in the obese phenotype. tallow, lard, corn oil, and hydrogenated coconut oil), along
The newly developed SHR/N-cp strain also retains the with 3.1% the American Institute of Nutrition vitamin
albino coat characteristic of the donor SHR strain, but not salt mix, and 1% Teklad vitamin fortification mix (control
the agouti coat of the LA/N-cp strain. In contrast, the F1 diet). The energy content of the diet was calculated to
hybrids retain elements of both coat characteristics. Both provide 48.2% of calories from carbohydrates, 33.3% from
phenotypes exhibit significantly reduced lifespans due fats, and 18.5% from protein, yielding 4.4 kcal/gram as
to complications of T2DM compared to their longevity- described elsewhere. 20-27 The semi-purified diet was fed
prone NIH (N) heritage. The independent contributions ad libitum for up to 8 weeks. In addition, the control diet
18
of the obesity and T2DM traits may be further assessed in was fortified with 150 mg of the α-glucosidase inhibitor
the non-diabetic LA/Ntul-cp and SHR/Ntul//-cp strains, (MIG) per kg of diet (equivalent to ~2.5 mg MIG/rat/
where T2DM has not been observed in the LA/Ntul//-cp day) and was fed to the α-glucosidase inhibitor treatment
strain to date, regardless of the diets offered. 17-20 Thus, the group for up to 8 weeks. Thus, both treatment groups
purpose of this investigation is to determine the efficacy consumed diets with the same proportions of essential
of therapeutic luminal inhibition of α-glucosidase activity nutrients and caloric density, with or without MIG. Body
through MIG on established insulin-linked parameters weights were monitored periodically throughout the study
of metabolism, including glycemic and lipid profiles, in a as an indicator of wellness. At the end of the study, rats
unique congenic animal model of early-onset obesity and were fasted overnight, and blood was obtained through
T2DM, in the absence of other confounding variables. In tail bleeding into heparinized tubes for plasma glucose
this animal model, the onset of comorbidities associated and insulin area under the glucose tolerance curve
with obesity and T2DM occurs soon after weaning in the (AUC) through a glucose oxidase method (250 mg/kg
obese phenotype of the strain. These conditions develop body weight, through gavage) on a YSI glucose analyzer
spontaneously due to an unknown mechanism, presumed and in-house radioimmunoassay, respectively. 28,29 Insulin

Volume 4 Issue 2 (2025) 61 doi: 10.36922/gtm.6501