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Older monkeys of the Sulawesian species Macaca nigra spontaneously develop a lesion in the pancreatic islets of Langerhans in which there is deposition of amyloid and gradual degeneration of all cells, which can lead eventually to development of diabetes mellitus. Islet cell antibodies (ICA), formed in response to the release of cellular antigens, can be used to detect the islet lesion and to monitor the progression of each monkey toward diabetes. Numerous M. nigra and one M. tonkeana in captivity have been tested, but it is unknown whether the islet lesion occurs in monkeys in their natural habitat of Sulawesi. Blood samples collected from M. maurus, M. tonkeana, and hybrid M. maurus/tonkeana were assayed for ICA. When all monkeys were considered together, 33% had ICA positive against beta cells and 14% had ICA positive against alpha and/or D cells. Appearance of ICA in blood of males was virtually the same as in females. These results are similar to those found in M. nigra examined in captivity. Since all Sulawesian species share a common genetic heritage, these results would support the appearance of this lesion in their natural habitat. Cause(s) for formation of the lesion and eventual development of diabetes are unknown. There may be genetic factors or genetic predisposition to environmental factors. If environmental factors are responsible, then they must be present not only in the wild, but either carried with the monkeys or universally available, since M. nigra born in captivity also develop the lesion and diabetes after physical maturity at ca. 7+ years.

A subset of Macaca nigra have been identified with elevated levels of fasting and secretory insulin. The insulin increment between 0 and 15 min in an intravenous glucose tolerance test (IV-GTT) was 511 +/- 42 microU/ml in hyperinsulinemic (HYPER) monkeys compared to 191 +/- 16 microU/ml in nondiabetic (ND) controls (p less than 0.01). Fasting insulin increased from 37 +/- 4 in ND to 57 +/- 7 microU/ml in HYPER monkeys (p = 0.02). Glucose clearance also increased from 3.87 +/- 0.18 in ND to 5.78 +/- 0.52%/min in HYPER monkeys (p less than 0.01). The acute (239 +/- 31 versus 137 +/- 19 microU/ml/min) and secondary insulin responses (542 +/- 75 versus 207 +/- 32 microU/ml/min) were significantly greater in the HYPER monkeys than in the ND controls, respectively (p less than 0.05). The rate of glucose clearance per amount of insulin secreted was diminished about 40% in both the acute and the secondary phases of HYPER monkeys (p less than 0.02). Total C-peptide secretion was two times greater in HYPER than in ND monkeys (p = 0.05). The HYPER monkeys averaged 12-20% greater weight and 41-44% greater body mass than the ND monkeys (p less than 0.05), although both groups were fed the same amount of diet and were well within nonobese limits. These Macaca nigra appear to have a functional lesion with excess insulin secretion, relatively impaired clearance of glucose, and possible insulin resistance, but no islet pathological lesion. Development toward overt diabetes might be exacerbated if obesity became a more dominant factor.

Results from studies with M. nigra allow some conclusions and predictions about the etiology and development of diabetes relative to the islet lesion in monkeys and human beings. Some factor or factors must initiate the lesion; whether this is genetic, environmental, or a combination of both is not known. Amyloid is not the initiating factor to the islet lesion, but appears later as there is deterioration of cells. Sufficient evidence does not yet exist to choose from among the alternatives regarding the source of amyloid. With gradual deterioration of cells and replacement by amyloid, secretion of insulin is impaired and concentrations of glucagon increase. Sufficient circulating insulin is probably chronically available to the cells in this moderately impaired state, so that an acute decrease in delta IRI in response to glucose in an iv-administered GTT does not cause significant impairment in glucose clearance. The increase in circulating glucagon is probably due to a loss of controls on alpha-cell secretion or synthesis of glucagon. Fasting glucose levels increase but remain within the nondiabetic range. Eventually there is sufficient accretion of amyloid, usually greater than 50%, so that substantial beta-cell loss occurs and the monkey can no longer maintain fasting normoglycemia. The monkey then is hyperglycemic and hypoinsulinemic. Only at this time are the impairments detectable by the usual diagnostic clinical criterion of hyperglycemia. The ICAs arise in response to secretory cell deterioration and are present until there no longer are sufficient cells to elicit an immune response. Results from M. nigra can give insight into a similar condition that probably exists in a subpopulation of older diabetic humans. Humans probably pass through stages similar to those discerned in monkeys. Nondiabetic humans with sufficient beta cells to sustain adequate secretion of insulin, but with moderate amyloid infiltration, probably would be in a category equivalent to BD monkeys; since these people are not overtly hyperglycemic, they are not clinically recognizable as diabetic and would be classified retrospectively as nondiabetic. Continued loss of cells with concomitant amyloid deposition would eventually lead to hyperglycemia; if examined at autopsy, these people would have visible islet amyloid as well as a retrospective diagnosis of diabetes. Older type II diabetic humans with ICA usually proceed to insulin therapy more rapidly than do those who are ICA negative (Irvine et al., 1977; Del Prete et al., 1977; Gray et al., 1980).(ABSTRACT TRUNCATED AT 400 WORDS)

The islets of Langerhans in sections from the pancreas tail of Macaca nigra were stained by antiserum to insulin, glucagon, or somatostatin. The area of stained cells per total area of the islets was determined by a computerized photometric method. Insulin of the beta cells occupied 77% of the islet area in nondiabetic (ND) monkeys and decreased to 62% in monkeys in the earliest stages of metabolic deterioration, i.e., hormonally impaired (HI) monkeys. At the later stage of borderline diabetes (BD), monkeys had only 39% of the islet area occupied by insulin and the area was diminished to less than 1% in diabetic (D) monkeys. Islets in HI monkeys had an unusual pattern in which only the beta cells in the periphery of islets were stained. Glucagon in the alpha cells stained 7% of the islet area in ND monkeys, but the area was almost doubled to 13% in HI monkeys; the percentage decreased to about 5% in BD and 3% in D monkeys. Somatostatin accounted for 5% of the islet area in ND monkeys, was slightly greater at 7% in HI monkeys, and decreased to 3% in BD and 2% in D monkeys. Alterations in percentages of secretory cells correlated with several of the metabolic and clinical changes.

Sections of pancreas from 21 nonhuman primates with diabetes mellitus were examined by light and electron microscopy. All monkeys showed amyloid accumulation in the islets of Langerhans. Amyloid was identified by its dichroism with three different stains: Congo red, changing from red to yellowish-green; standardized toluidine blue, changing from blue to red; and sulfated alcian blue, changing from blue-green to pink. Sulfated alcian blue was a rapid and effective means of detecting amyloid. The characteristic fibrillar structure of amyloid was seen with transmission electron microscopy. Deposition of islet amyloid was independent of the presence or absence of amyloid in other organs. Results indicate that nonhuman primates offer a model for studying the sequential development of insular amyloidotic diabetes mellitus.

Aortic atherosclerosis is minimal in normal Macaca nigra; development of atherosclerosis correlates with increasing severity of diabetes mellitus. The extent of aortic involvement (plaque plus sudanophilia) was quantified and compared with metabolic and clinical parameters. Increasing atherosclerosis correlated with decreasing ability to clear glucose in a tolerance test (P less than 0.01), decreasing insulin (P = 0.02), and increasing glucose (P less than 0.01) and triglycerides (P less than 0.01). A diabetic index, established as a summation of several metabolic measurements, correlated with atherosclerosis at P less than 0.001. On the average, involvement of the thoracic aorta was about 3-fold greater than in the abdominal portion; involvement reached over 40% in severely diabetic monkeys. Atherosclerosis development is unique in these monkeys since they consume a natural ration low in fat and cholesterol. Serum cholesterol did not correlate with diabetes or artherosclerosis. Increasing age alone was associated with slight sudanophila, some intima-media thickening, and occasional small lesions. However, only with increasing severity of diabetes was there significant atherosclerosis.

Serum proteins of Macaca nigra were separated by agarose gel electrophoresis. Proteins identified were: albumin, alpha 1-globulin, alpha 2-macroglobulin, haptoglobin, beta 1C-globulin, and gamma 1- and gamma 2-globulins. Diabetic M. nigra had decreased gamma 2-globulin; borderline diabetics had increased beta 3-globulin.

Glucose intolerance was found in four adult chimpanzees. The response of glucose, insulin, C-peptide, and glucagon to intravenous glucose and tolbutamide stimulations revealed impaired glucose clearance, deficient pancreatic secretion of insulin and C-peptide, and elevated glucagon levels. Pancreatic islets in a diabetic chimpanzee were hypercellular, possible due to alpha-cells. Minimal or no insulin was observed in beta-cells. Results are consistent with the occurrence of noninsulin-dependent diabetes mellitus, which may be more prevalent in chimpanzees than heretofore suspected.

The thickness of the capillary basement membrane of femoral muscle was examined in normal and spontaneously diabetic Macaca nigra. Thickness correlated significangly with the degree and severity of diabetes; greater thickness was associated with decreased glucose tolerance, decreased serum insulin, and increased glucose and triglyceride. In normal monkeys, the average basement membrane thickness was 696 A and in diabetic monkeys, 837 A, The minimum basement membrane thickness was 524 A in normal monkeys and 634 A in diabetics. Normals differed significantly from diabetic monkeys.

Sections of pancreas from 21 nonhuman primates with diabetes mellitus were examined by light and electron microscopy. All monkeys showed amyloid accumulation in the islets of Langerhans. Amyloid was identified by its dichroism with three different stains: Congo red, changing from red to yellowish-green; standardized toluidine blue, changing from blue to red; and sulfated alcian blue, changing from blue-green to pink. Sulfated alcian blue was a rapid and effective means of detecting amyloid. The characteristic fibrillar structure of amyloid was seen with transmission electron microscopy. Deposition of islet amyloid was independent of the presence or absence of amyloid in other organs. Results indicate that nonhuman primates offer a model for studying the sequential development of insular amyloidotic diabetes mellitus.

Spontaneous diabetes mellitus was reported in a Mandrillus leucophaeus (drill baboon) and a Mpacaca cyclopis (Formosan rock macaque). Each had hyperglycemia, impaired clearance of glucose during tolerance test, and reduced concentrations of immunoreactive insulin; the M cyclopis also had increased triglyceride and prebetalipoprotein concentrations. Both monkeys had extensive amyloid infiltration into the islets of Langerhans and loss of beta cells. Beta cell obliteration can account for the appearance of the diabetic syndrome in these and other nonhuman primate species.

Amyloid was isolated from islets of amyloidotic pancreata of monkey and human beings by solubilization of non-amyloid materials from the pancreas and digestion of contaminating collagen and elastin. The resulting pellet was estimated to be greater than 90% pure islet amyloid. Antibodies specific for monkey islet amyloid and for monkey and human liver amyloid A (AA) were raised in rabbits. Immunohistochemical reaction using the peroxidase antiperoxidase method demonstrated that amyloidotic pancreas reacted with both anti-AA and anti-islet amyloid antibodies. Although the antibodies are specific toward antigens, they cross-react with tissues from human and monkeys. The immunochemical results suggest the possibility that more than one kind of amyloid is associated with islet amyloidosis, but that a significant portion of the islet amyloid is related to AA. Preliminary chemical analysis indicated that islet amyloid is enriched with hexosamines while AA contains both hexosamines and hexoses. Establishment of the islet amyloid composition(s) can give insight into its source and its role in diabetes in Macaca nigra and human beings.

Dietary fat affects serum lipids independently of dietary cholesterol. Normal and diabetic monkeys (Macaca nigra) were fed cereal-based, specially formulated diets with either a low fat (LF = 2.5%) or a higher fat (13.2%) content; the latter had varying concentrations of safflower and coconut oil to attain greater polyunsaturation (SFO) or saturation (CCO) in the diets. Dietary cholesterol was less than 0.01%. Serum triglyceride concentrations were greatest when monkeys consumed the LF (higher carbohydrate) diet and lowest when they consumed the SFO diet. Concentrations were greater in diabetic than in normal monkeys fed the LF and SFO diets, but both groups had similar concentrations when fed the CCO diet. Cholesterol levels in diabetic monkeys were only slightly higher than in normals regardless of diet; in both groups, levels were lowest when the LF diet was fed and highest when the CCO diet was fed. The quantity of fat had a greater effect on serum cholesterol than did the degree of polyunsaturation. In both groups, triglyceride concentrations correlated significantly with VLDL protein, and cholesterol levels correlated with LDL protein. Thus the responses of Macaca nigra to dietary fat manipulation depend upon both the diet fat content and composition as well as the normal or diabetic metabolic state of each monkey.

Development of spontaneous diabetes has been monitored in individual Macaca nigra. In this study, pancreatic biopsies were taken, islets were assessed morphologically, and results were related to the metabolic/clinical status. A biopsy or autopsy sample was obtained 4 to 10 years later, and the islet morphological state was again related to the metabolic/clinical status. Metabolic deterioration was correlated to the islet lesion, in which there was gradual loss of islet secretory cells and concurrent amyloid deposition. As nondiabetic monkeys with 0 to 3% islet amyloid progressed up to 20 to 40% amyloid, the insulin secretion and glucose clearance were both decreased (p less than or equal to 0.01), and the glucose and glucagon levels increased (p = 0.05). Impaired monkeys progressed to overt diabetes when islet amyloid exceeded 50 to 60%. Diabetic monkeys developed hyperglycaemia, along with impaired insulin secretion and glucose clearance (p less than 0.01). Loss of islet cells results in metabolic deterioration. The lesion precedes development of overt diabetes in Macaca nigra.