Islet organ, blood glucose and glucose tolerance of lean and obese Mongolian gerbils. A quantitative study

Gerbils were divided, on the basis of body weight, into obese (greater than 80 gms) and lean (less than 80 gms) groups. Fasting blood glucose estimations on all 31 gerbils, and glucose tolerance tests on 9 lean and 6 obese animals, were carried out. All lean and some obese gerbils were normoglycaemic and other obese were hyperglycaemic. All obese gerbils exhibited glucose intolerance. General morphological studies were undertaken as follows: (i) assessment of mesenteric fat deposits, (ii) measurement of anterior abdominal wall thickness, (iii) ratio of animal length to width at specified loci (index of shape). The degree of obesity was less than previously reported in this species though blood glucose abnormality was comparable. The index of animal shape showed a strong correlation with body weight. The following kinds of histological observation were made on pancreases from 4 lean and 4 obese gerbils: (i) % islet representation, (ii) islet size distribution, (iii) beta-cell granularity, (iv) islet vascularity, (v) islet/duct association, (vi) proportions of alpha- and D-cells, (vii) glycogen deposition in islet and duct cells. The pancreases of obese gerbils contained a higher proportion of islet tissue than those of lean due to generally larger islets: this hyperplasia was mainly attributable to beta-cell proliferation. Many obese gerbil islets exhibited hyperaemia and beta-cell degranulation. There was no evidence of glycogen deposition.