Immunohistochemical investigations of the endocrine pancreas in normoglycemic sand rats (Psammomys obesus)

Metabolic consequences of a 50% partial pancreatectomy in humans

AIMS/HYPOTHESIS

Partial pancreatectomy is frequently performed in patients with pancreatic tumours or chronic pancreatitis, but little is known about the metabolic impact of this intervention. We examined the effects of approximately 50% partial pancreatectomy on glucose homeostasis and insulin secretion.

METHODS

Fourteen patients with chronic pancreatitis, ten patients with pancreatic carcinoma and 13 patients with benign pancreatic tumours or extra-pancreatic masses (control group) underwent 240 min oral glucose tolerance tests before and after pancreatic tail-resection (n = 12), duodenopancreatectomy (n = 19) or duodenum-preserving pancreatic-head resection (n = 6).

RESULTS

Partial pancreatectomy led to a reduction in post-challenge insulin excursions by 49% in chronic pancreatitis patients, 52% in carcinoma patients and 55% in controls (p < 0.05). Nevertheless, post-challenge glucose concentrations were transiently ameliorated after surgery (p < 0.001). In the control participants, pancreatic-head resection caused a transient reduction of post-challenge glycaemia, whereas pancreatic-tail resection increased both fasting and post-challenge glycaemia (p < 0.05). Insulin sensitivity was highest in chronic pancreatitis patients before surgery (p < 0.01), but remained unchanged by the partial pancreatectomy. High pre-operative body weight and elevated fasting glucose levels were associated with poor glycaemic control after surgery.

CONCLUSIONS/INTERPRETATION

Insulin secretion is diminished after pancreatic-head and -tail resection, but post-challenge glucose concentrations can be ameliorated after pancreatic-head resection. These data highlight the unequal impact of different surgical procedures on glucose control and suggest that obesity and high pre-operative glucose levels should be considered as risk factors for the development of hyperglycaemia after pancreatic surgery.

An immunohistochemical study of the endocrine pancreas of the African ice rat, Otomys sloggetti robertsi

The African ice rat, Otomys sloggetti robertsi, is a member of the subfamily Otomyinae, in the superfamily of Muroidea, to which all rodents belong. Very little is known about this unique family of rodents. The study reported here examines the endocrine pancreas of this species using immunohistochemical techniques. The islets of Langerhans were scattered in the exocrine pancreas and tended to be quite small. Scattered single endocrine cells (mostly immunoreactive for insulin) were found in the exocrine pancreas and were not generally associated with ducts (as marked by pan-cytokeratin labeling). The normal islet architecture of insulin in the center and glucagon, somatostatin (SS) and pancreatic polypeptide (PP) in the rim was observed, but the islets tended to have 2-3 layers of glucagon immunoreactive cells. Examining for rarer endocrine cell types, we found that cocaine amphetamine regulated transcript (CART) immunoreactive cells were co-localized with SS; and peptide YY (PYY) immunoreactive cells could be found that were singly immunoreactive or co-localized with either PP or glucagon. Ghrelin cells were not found. MafA co-localized only with the insulin cells, while MafB, which localizes to the glucagon cells, also showed a low level of immunoreactivity in most insulin immunoreactive cells. The Nkx family of transcription factors (Nkx6.1 and 2.2) and PDX-1 were all detected in the pancreas in a similar manner to that seen in mouse and rat. In conclusion, the endocrine pancreas of the African ice rat is quite similar to that of other studied rodents, but these animals have more glucagon and SS cells than rat (Rattus) or mouse (Mus) species.

Developmental Biology of the Psammomys obesus Pancreas: Cloning and Expression of the Neurogenin-3 Gene

The desert gerbil Psammomys obesus, an established model of type 2 diabetes (T2D), has previously been shown to lack pancreatic and duodenal homeobox gene 1 (Pdx-1) expression. Pdx-1 deficiency leads to pancreas agenesis in both mice and humans. We have therefore further examined the pancreas of P. obesus during embryonic development. Using Pdx-1 antisera raised against evolutionary conserved epitopes, we failed to detect Pdx-1 immunoreactivity at any time points. However, at E14.5, Nkx6.1 immunoreactivity marks the nuclei of all epithelial cells of the ventral and dorsal pancreatic buds and the only endocrine cell types found at this time point are glucagon and PYY. At E18.5 the pancreas is well branched and both glucagon- and ghrelin-positive cells are scattered or found in clusters, whereas insulin-positive cells are not found. At E22.5, the acini of the exocrine pancreas are starting to mature, and amylase and carboxypeptidase A immunoreactivity is found scattered and not in all acini. Ghrelin-, glucagon-, PYY-, gastrin-, somatostatin (SS)-, pancreatic polypeptide (PP)-, and insulin-immunoreactive cells are found scattered or in small groups within or lining the developing ductal epithelium as marked by cytokeratin 19. Using degenerate PCR, the P. obesus Neurogenin-3 (Ngn-3) gene was cloned. Nucleotide and amino acid sequences show high homology with known Ngn-3 sequences. Using specific antiserum, we can observe that Ngn-3-immunoreactive cells are rare at E14.5 but readily detectable at E18.5 and E22.5. In conclusion, despite the lack of detection of Pdx-1, the P. obesus pancreas develops similarly to Muridae species, and the Ngn-3 sequence and expression pattern is highly conserved in P. obesus.

The Harderian gland in diabetic sand rats (Psammomys obesus) a light microscopic study

The purpose of this study was to examine the long-term effects of synthetic diet on the sand rat Harderian gland. From the third month, animals showed a diabetic syndrome characterized histologically by Harderian gland necrotic changes. Some gland tubules and melanocytes were disintegrated and numerous mast cells were densely populated in the connective capsule of the gland. Moreover, luminal porphyrin accretions and cellular debris were often associated with alcian blue positive materials. If the synthetic diet lasted more than 6 months, the gland was strongly damaged and numerous plasma cells, macrophages, and lymphocytes infiltrated the gland. These results clearly demonstrate that the sand rat Harderian gland is affected by the diabetic syndrome induced by the synthetic diet.

Seasonal variations in the function of the endocrine pancreas in Psammomys obesus

The aim of this work was to determine whether Psammomys obesus living in its natural habitat displays variation in the function of the endocrine pancreas. Live animals were collected regularly through the year by strip sampling. Plasma glucose varied during the year. Glucose levels were higher in periods I and III (autumn and spring) than in periods II and IV (winter and summer). Pancreatic insulin contents were higher in periods I and II than in periods III and IV. Plasma insulin also varied with the season in synchrony with glucose variations except during period IV, in which elevated levels of insulin were associated with low levels of glucose. The high insulin levels observed in period IV were resistant to the effects of food restriction in that period and were probably related to the presence of the greater levels of insulin in period III (spring). The dry season (period IV) corresponding to the period of restricted diet appears necessary to restore elevated levels of insulin to baseline. Morphometric quantitation of the insulin, glucagon, and somatostatin positive islet cells did not reveal seasonal variation. However, the volume density of A and D cells in P. obesus reached high values of 32 and 15%, respectively. The volume density of insulin cells amounted to about 53%. It is concluded that P. obesus living in its natural habitat is a nondiabetic healthy gerbil adapted to desert subsistence by endocrine feedback, imposed by the seasonal variation in food availability.