Differential effects of ambient blood glucose level and degree of obesity on basal serum C-peptide level and the C-peptide response to glucose and glucagon in non-insulin-dependent diabetes mellitus

We student basal, glucose- and glucagon-induced insulin secretion in non-insulin diabetes mellitus (NIDDM) patients in relation to body mass index (BMI) and fasting serum glucose (FBS) level. A total of 46 NIDDM patients and 22 control subjects with varying degrees of BMI and FBS were given 100 g of oral glucose and 1 mg of intravenous glucagon on separate days. C-peptide response to glucose, but not basal serum C-peptide and C-peptide response to glucagon, was significantly lower in NIDDM than in controls (P < 0.001). FBS was inversely correlated with C-peptide response to glucose in NIDDM patients (r = -0.67, P < 0.001), but not with basal C-peptide level and C-peptide response to glucagon. On the other hand, BMI was positively correlated with basal serum C-peptide level both in NIDDM (r = 0.60, P < 0.001) and in control subjects (r = 0.74, P < 0.001). In 15 poorly controlled NIDDM patients, the tests were repeated after insulin treatment for 10-14 days. C-peptide response to glucose significantly increase, but not to a level in control subjects, after glycemic control. Basal serum C-peptide level and the C-peptide response to glucagon decreased after glycemic control to significantly lower levels than those in the baseline and those in control subjects. These results suggest that beta cell secretory reserve is reduced in moderate to severe NIDDM patients.

Involvement of different second messengers in parathyroid hormone- and interleukin-1-induced interleukin-6 and interleukin-11 production in human bone marrow stromal cells

Previous studies have suggested that increased secretion of bone active cytokines, such as interleukin-6 (IL-6) and interleukin-11 (IL-11), from osteoblasts and stromal cells play a pivotal role in the activation of osteoclasts and the genesis of osteoporosis. Various systemic and local factors can stimulate IL-6/IL-11 production, but the intracellular mechanism for such stimulation is largely unknown. In this study, we characterized the second messenger signaling in parathyroid hormone (PTH)- and IL-1-induced production of IL-6/IL-11 and studied the possible modulating effects of estrogen. rhPTH(1-34) and rhIL-1 alpha dose-dependently stimulated IL-6 and IL-11 production from human bone marrow stromal cells (hBMSCs). Agonists for protein kinase A (PKA) (forskolin), and protein kinase C (PKC) (phorbol 12-myristate 13-acetate; PMA) also stimulated IL-6/IL-11 production. Rp-diastereoisomer of adenosine cyclic 3',5'-phosphorothioate (Rp-cAMPS) and H-8, inhibitors of PKA, significantly inhibited PTH-stimulated IL-6/IL-11 production, but did not inhibit IL-1-stimulated IL-6/IL-11 production. In contrast, staurosporine and calphostin C, inhibitors of PKC, suppressed IL-1-stimulated, but not PTH-stimulated, IL-6/ IL-11 production. Pretreatment of cells with 17 beta-estradiol (17 beta-E2) antagonized IL-1-stimulated IL-6 production. However, PTH-stimulated IL-6 production and IL-1- and PTH-stimulated IL-11 production were not affected by 17 beta-E2. Similarly, 17 beta-E2 inhibited PMA-stimulated IL-6 production, whereas neither forskolin-stimulated IL-6/ IL-11 production nor PMA-stimulated IL-11 production was affected by 17 beta-E2. These results indicate that different second messengers are involved in PTH- and IL-1-induced IL-6 and IL-11 production by hBMSCs: PTH and IL-1 stimulate IL-6/IL-11 production via a PKA-dependent and PKC-dependent pathway, respectively. Furthermore, our results suggest that regulation of cytokine production by estrogen in hBMSCs is selective; only the IL-1-induced IL-6 production, which is mediated by PKC pathway, is inhibited, but PTH-induced IL-6 production and PTH/IL-1-induced IL-11 production are not inhibited by estrogen.

Paget bone disease involving young adults in 3 generations of a Korean family

Although the etiology of Paget bone disease (PBD) is unknown, increasing evidence implicates a "slow virus" infection of the skeleton, perhaps in genetically predisposed individuals. PBD is rare in Asia. We describe a Korean family with PBD. The propositus noticed bowed limbs at approximately 25 years of age. Radiologic studies made when he was 55 years old revealed essentially panostotic PBD. Serum alkaline phosphatase (ALP) activity and osteocalcin (OC) levels were markedly elevated. An iliac crest specimen showed classic histopathologic changes of PBD. Additionally, palpable swellings were first observed at age 45 years at his occiput, pubic ramus, ileum, and facial bones. They contained numerous multinucleated cells and were originally diagnosed as giant cell tumors. However, we found that, like osteoclasts, these cells expressed considerable tartrate-resistant acid phosphatase activity. These "extraskeletal osteoclastomas" resolved rapidly with dexamethasone treatment. Two daughters, 20- and 24-years-of-age, were discovered by study of his 5 children to have elevated serum ALP activity and OC levels and widespread PBD. Both women, however, are without palpable masses and are asymptomatic. The propositus' father, who died at age 55 years, had similar skeletal deformities beginning at age 20 years, but was not examined. Leukocytopenia was found in the 3 living family members with PBD. There was no evidence for linkage of the PBD to HLA loci. The condition appears to be transmitted as an autosomal dominant trait and is manifest in young adult life. Multicentric extraskeletal osteoclastomas with remarkable sensitivity to dexamethasone treatment appear to be another unusual feature of this family's disorder. In this family, the stimulus for PBD is so great that the PBD is apparent at an early age, affects essentially the entire skeleton, and leads to the formation or extension of osteoclast-like cells into nonosseous tissues (extraskeletal osteoclastomas). This 3-generation kindred in Korea, where PBD is rare, shows a strong clustering of PBD compatible with autosomal dominant inheritance. Leukocytopenia appears to distinguish affected family members, but any role for this abnormality in the pathogenesis of PBD is unclear. Our findings support a heritable diathesis for PBD, perhaps mediated by an immune deficiency.

Mutation of ras oncogene in gastric adenocarcinoma: association with histological phenotype

In order to explore the role of ras oncogene in gastric carcinomas from Korean patients, we examined the frequency of point mutations all three ras oncogenes (Ki-, Ha-, and N-ras). A total of 57 DNA samples were prepared from 3 gastric carcinoma cell lines, 10 malignant ascites, and 44 frozen gastric tumor tissues. Exons 1 and 2 of each ras oncogene were amplified by polymerase chain reaction (PCR), and analyzed by single strand conformation polymorphism (SSCP) and direct sequencing. Mutated ras genes were detected in 6 out of 57 samples (10%). One cell line and 2 tumors showed a mutation at exon 1 of Ki-ras. N-ras mutations were also detected at exon 1 of 3 tumors. Histologically, all the ras mutation cases exhibited a diffuse phenotype. In summary, we performed a comprehensive analysis to investigate the mutation of all three ras oncogenes in gastric carcinoma. The results demonstrate infrequent mutations of Ki- and N-ras which may favor the development of diffuse type gastric carcinomas, implicating a different genetic pathway in diffuse and intestinal type gastric carcinomas.

Past and current obesity in Koreans with non-insulin-dependent diabetes mellitus

To determine the prevalence of past and current obesity among patients with non-insulin-dependent diabetes mellitus (NIDDM) and to define the clinical characteristics of non-obese NIDDM patients in South Korea, we studied a cross-section of 749 NIDDM patients and a group of age- and sex-matched control subjects. Current height, weight and waist-to-hip ratio (WHR), the history of weight changes and the family history of diabetes were recorded. Obesity was defined as body mass index (BMI) > 25 kg/m2. The maximum lifetime BMI of diabetic patients was significantly higher than that of control subjects (P < 0.001). Compared with control subjects, current BMI was higher in diabetic women (P < 0.001) but not in diabetic men. In contrast, WHR of both diabetic men and women were significantly higher than those of controls (P < 0.05). BMI and WHR correlated significantly with fasting C-peptide levels and log-triglyceride levels in NIDDM patients. As a whole, 72% of the South Korean NIDDM patients had a history of past obesity as assessed by their maximum weight, while only 38% of them were currently obese. Compared with obese patients, non-obese patients were characterized by lower fasting serum C-peptide levels (P < 0.001), a higher percentage of insulin treatment (P < 0.05), lower maximum BMI (P < 0.001) and more pronounced weight loss from the time at their maximum weight (P < 0.001). In summary, increased upper body adiposity and a history of past obesity were associated with NIDDM in South Korea. Although most South Korean NIDDM patients were previously obese, many of them were currently not obese. Lower maximum BMI, lower serum C-peptide levels and a higher percentage of insulin treatment in non-obese NIDDM patients suggest that the capacity to increase insulin secretion in response to increasing weight gain is rather limited in these patients.

Preoperative evaluation of the curative resectability of gastric cancer by abdominal computed tomography and ultrasonography: a prospective comparison study

OBJECTIVES

We compared the ability of preoperative abdominal computed tomography (CT) with that of preoperative abdominal ultrasonography (US) in predicting the extent of tumor growth and the curative resectability of gastric cancer.

METHODS

Abdominal CT and US were done in 95 patients with gastric adeno-carcinoma. The radiologic findings were prospectively compared with surgical and pathologic findings.

RESULTS

The sensitivities of abdominal CT and US in detecting the perigastric lymph node involvement were 26.6% and 20%, respectively. The sensitivity of abdominal CT in predicting the pancreatic invasion (60%) was better than that of abdominal US (20%). However, there were 6 false positive diagnosis of pancreatic invasion by abdominal CT; in contrast, there was no false positive diagnosis of pancreatic invasion by abdominal US. Of 95 patients who underwent surgical exploration, 14 were found to have unresectable tumors because of extragastric organ involvement and distant metastases. Abdominal CT falsely predicted 8 of 14 cases in which curative gastric resection was impossible as resectable. Moreover, abdominal CT falsely predicted 5 of 81 cases in which curative gastric resection was possible as unresectable. Abdominal US falsely predicted 12 of 14 cases in which curative surgery was impossible as resectable.

CONCLUSION

Preoperative abdominal Ct and US did not accurately predict the tumor extent and the curative resectability of the gastric cancer. Especially, abdominal CT finding of pancreatic invasion by gastric cancer should not be a contraindication for surgical exploration.

Effects of vitamin B12 on cell proliferation and cellular alkaline phosphatase activity in human bone marrow stromal osteoprogenitor cells and UMR106 osteoblastic cells

Pernicious anemia has recently been recognized as one of the risk factors for osteoporosis and bone fractures, but the underlying pathophysiologic mechanism is still unknown. To determine whether vitamin B12 has any direct effect on osteoblasts, we studied the effects of vitamin B12 on the proliferation and alkaline phosphatase activity in human bone marrow stromal osteoprogenitor cells (hBMSC) and UMR106 osteoblastic cells. Vitamin B12 at concentrations as low as 10(-12) mol/L significantly stimulated [3H]-thymidine incorporation in both types of cells, but concentrations higher than 10(-12) mol/L did not produce a greater effect. Vitamin B12 in the concentration range from 10(-12) to 10(-8) mol/L concentration-dependently increased alkaline phosphatase activity in both hBMSC and UMR106 cells. Based on these results, we suggest that a suppressed activity of osteoblasts may contribute to osteoporosis and fractures in patients with vitamin B12 deficiency.

Effect of decreasing plasma free fatty acids by acipimox on hepatic glucose metabolism in normal rats

Increased availability of free fatty acids (FFA) may play a role in the pathogenesis of insulin resistance in the liver. We examined the effects of an antilipolytic nicotinic acid analog (acipimox) on hepatic glucose metabolism in basal and hyperinsulinemic states in normal rats. Acipimox decreased plasma FFA levels profoundly and enhanced the ability of insulin to suppress hepatic glucose production (HGP) and to stimulate peripheral glucose utilization. In the basal state, acipimox inhibited hepatic gluconeogenesis. However, this inhibition was not associated with the change in overall HGP due to the compensatory increase in hepatic glycogenolysis that might occur as a consequence of decreased hepatic glucose-6-phosphate (G-6-P) and/or plasma insulin levels with acipimox. These results support the contention that FFA are an important determinant of insulin action in the liver, and suggest the existence of intrahepatic autoregulatory and/or hormonal regulatory processes for constant HGP in the basal state.

Glomerular hyperfiltration in Koreans with non-insulin-dependent diabetes mellitus

Glomerular hyperfiltration (GHF) may play an important role in the pathogenesis of diabetic nephropathy. The prevalence of GHF in non-insulin-dependent diabetes mellitus (NIDDM) is reported to vary in different populations, ranging from 35% in black Americans with new-onset diabetes to less than 5% in whites. We measured glomerular filtration rate (GFR) by 51Cr-EDTA clearance methods in 284 Korean NIDDM patients without overt nephropathy. Glomerular hyperfiltration (defined as GFR > 140 mL/min/1.73 m2) was found in 25% (71 of 284) of the patients. Thirty percent and 15% of the patients with known duration of diabetes less than 5 years and more than 10 years, respectively, showed GHF. Microalbuminuria (defined as urinary albumin excretion rate 20 to 200 micrograms/min) was found in 23% (64 of 284) of the patients. The mean GFR of the microalbuminuric patients was not significantly different from that of the normoalbuminuric patients (121.5 +/- 30.1 mL/min/1.73 m2 v 124.9 +/- 26.4 mL/min/1.73 m2; P = NS). However, when the patients with microalbuminuria were divided according to the presence or absence of retinopathy, the microalbuminuric patients with retinopathy had a lower GFR compared with the microalbuminuric patients without retinopathy (109.6 +/- 35.5 mL/min/1.73 m2 v 130.0 +/- 26.3 mL/min/1.73 m2; P < 0.01). These results show that the prevalence of GHF in Korean NIDDM patients without overt nephropathy is higher than that reported in whites and that it is similar to that in black Americans. The high prevalence of GHF in Korean NIDDM patients may contribute to the relatively higher prevalence of clinical diabetic nephropathy in this population.

Characterization of cell lines established from human hepatocellular carcinoma

We characterized 8 human hepatocellular-carcinoma cell lines established from the primary tumors of Korean patients. All lines showed substrate adherence and one line from anaplastic tumor also grew as floating aggregates. Most cultured cells maintained many morphological characteristics of the original tumors from which they were derived. Doubling times varied from 34 to 72 hr. All lines showed relatively high viability and were not contaminated with Mycoplasma or bacteria. All lines showed aneuploidy and were proven to be unique by DNA fingerprinting analysis. Hepatitis-B-virus (HBV) DNA was integrated in the genomes of all lines. Two of the cell lines (SNU-354, SNU-368) showed expression of HBV and HBVx (HBx) transcripts. SNU-354 strongly expressed albumin, and SNU-368 expressed transferrin and insulin-like growth factor II. No lines produced alpha-fetoprotein at the RNA and protein level. These cell lines represent useful tools for in vitro studies related to hepatocellular carcinoma.

Prevalence and associated features of albuminuria in Koreans with NIDDM

OBJECTIVE

To determine the prevalence and the associated features of microalbuminuria and overt proteinuria in Korean subjects with non-insulin-dependent diabetes mellitus (NIDDM) attending a hospital clinic.

RESEARCH DESIGN AND METHODS

A total of 631 Korean outpatients with NIDDM were studied cross-sectionally for the presence of albuminuria and other micro- and macrovascular complications. Urinary albumin excretion rate (AER) was determined in timed overnight urine samples. Subjects were divided into three groups: no nephropathy (AER < 20 micrograms/min), microalbuminuria (AER 20-200 micrograms/min), and overt proteinuria (AER > 200 micrograms/min).

RESULTS

Increased AER was present in 34% of our patients: 20% had microalbuminuria and 14% had overt proteinuria. Of patients with diabetes duration > or = 15 years, 35% had overt proteinuria. Most (82%) patients with overt proteinuria had retinopathy. Although the prevalence of microalbuminuria as a whole did not differ according to diabetes duration, the prevalence of microalbuminuria in the patients with retinopathy increased with diabetes duration. The microalbuminuric patients without retinopathy (diabetes duration < 5 years) were characterized by higher prevalence of hypertension and previous obesity, higher plasma triglyceride level, and lower plasma high-density lipoprotein cholesterol level.

CONCLUSIONS

The prevalence of overt proteinuria in Korean NIDDM patients with a long diabetes duration was higher than that reported in Caucasians. Our data also suggest that the clinical meaning of microalbuminuria may be different based on the presence or the absence of retinopathy. Microalbuminuria in patients with retinopathy most probably would reflect diabetic nephropathy. In contrast, some recent-onset NIDDM patients with microalbuminuria in the absence of retinopathy had features of syndrome X.

Clinical heterogeneity of insulin dependent diabetes mellitus in Korea

This study was undertaken to find out how many current Korean patients with insulin dependent diabetes mellitus (IDDM) had a previous history of non-insulin requiring phase. Fasting serum C-peptide levels were measured in the 2300 diabetic patients during the visit to the Asan Medical Center, Seoul, Korea. Fifty-nine patients showed fasting serum C-peptide levels below 0.13 nmol/l. These 59 patients were classified further into two groups according to their history of insulin requirement: group A who required insulin within 1 year after diagnosis or presented initially as diabetic ketoacidosis and group B who had non-insulin requiring phase at least for 1 year (median: 5 years; range: 1-23 years). Twenty-six patients (44%) were classified into group A and 27 patients (46%) into group B. Median age of onset was 26 years (range: 10-50 years) and 45 years (range: 23-73 years) in groups A and B, respectively (P < 0.001). While the two groups had similar values in the current and maximum body mass indices, sex ratio and the prevalence of islet cell antibodies, 58% of the group A and 7% of the group B patients had histories of diabetic ketoacidosis. These results suggest a clinical heterogeneity in patients with IDDM in Korea.

Nitric oxide produced by macrophages mediates suppression of ConA-induced proliferative responses of splenic leukocytes in the diabetes-prone BB rat

Splenic cells from the diabetes-prone BB rat show reduced proliferative responses to concanavalin A (ConA) and other mitogens. This study was undertaken to test whether this reduced lymphoproliferation in the BB rat is mediated by an increased production of nitric oxide (NO) by macrophages. Splenic leukocytes from diabetes-prone BB rats and five strains of control rats (BB-R, Wistar-Furth, Sprague-Dawley, Wistar, and Lewis) were cultured in RPMI-1640 media containing ConA. The leukocytes from BB rats showed reduced [3H]thymidine uptake and increased release of NO compared with the control rats. Partial depletion of macrophages from the culture or incubation with -NG-monomethylarginine (NGMMA), a specific NO synthase inhibitor, markedly augmented ConA-induced proliferation of the splenic leukocytes from BB but not the control rats. Enrichment of BB rat macrophages suppressed the proliferation of BB-R rat spleen cells. Excess L-arginine added to the culture reversed the NGMMA effect. These results suggest that increased production of NO by macrophages is partly responsible for the reduced proliferative responses of splenic leukocytes in the BB rat.

Intra-abdominal fat is associated with decreased insulin sensitivity in healthy young men

To distinguish the relative role of intra-abdominal and subcutaneous abdominal fat in metabolic aberrations in upper body fat localization, we measured the relationship between regional fat distribution and insulin sensitivity in nine young men (28.6 +/- 0.7 years; body mass index [BMI], 24.7 +/- 1.3 kg/m2). Regional fat distribution was measured by anthropometric measurement and computed tomography (CT). Insulin sensitivity was measured by euglycemic hyperinsulinemic glucose clamp. Insulin sensitivity, expressed as the ratio of rate of glucose utilization to the mean plasma insulin concentration during the second hour of glucose clamp (M/I) was negatively correlated with BMI (r = -.91, P less than .001), waist to hip girth ratio (WHR) (r = -.80, P less than .01), subcutaneous abdominal fat area (r = -.90, P less than .001), and intra-abdominal fat area (r = -.88, P less than .01). Stepwise forward regression analysis showed that in addition to BMI, intra-abdominal fat area was a significant correlate of decrease in insulin sensitivity. These findings suggest that intra-abdominal fat play an important role in decreasing insulin sensitivity, even in healthy young men.

Studies on autoimmunity for initiation of beta-cell destruction. VII. Evidence for antigenic changes on beta-cells leading to autoimmune destruction of beta-cells in BB rats

The diabetic syndrome in BioBreeding (BB) rats is believed to result from the destruction of beta-cells by autoimmune responses. However, the initial events that cause the autoimmune destruction of beta-cells remain largely unknown. This investigation was initiated to see whether there are any antigenic changes on the beta-cells from neonatal to adult BB rats that may lead to the autoimmune destruction of beta-cells. Pancreatic grafts from neonatal BB rats remained largely intact without insulitis when transplanted into the renal subcapsular space of acutely diabetic BB rats. Similarly transplanted islet grafts from neonatal BB rats were also not subject to autoimmune destruction. In contrast, islet grafts obtained from adult BB rats, which had been treated with silica to prevent insulitis, were rapidly destroyed in diabetic recipients. These results indicate that beta-cells from neonatal BB rats are different from beta-cells from adult BB rats, at least regarding their recognition by immunologic effectors. Considering our observations and previous information on the initial role of macrophages/dendritic cells in the development of insulitis in BB rats, we suggest that beta-cell-specific antigenic changes that precede insulitis may result in the autoimmune destruction of beta-cells in BB rats.

Predisposing effect of anti-beta cell autoimmune process in NOD mice on the induction of diabetes by environmental insults

In NOD mice. 50-70% of females and 10-20% of males develop diabetes, although almost all the animals show insulitis. To see if environmental insults could induce diabetes in subjects with pre-clinical anti-Beta cell autoimmunity, non-diabetic NOD mice were selected and injected with a sub-diabetogenic dose of streptozotocin at 6 or 20 weeks of age. The streptozotocin failed to induce diabetes in 16 male and 16 female NOD mice within 4 weeks when they were injected at the age of 6 weeks. In contrast, 6 of 16 male and 10 of 16 female NOD mice developed diabetes within 4 weeks when they were injected at the age of 20 weeks. In untreated age-matched control NOD mice, none of the male and only 2 of 16 female mice became diabetic during the same 4 week period. On histologic examination, the degree of insulitis in streptozotocin-treated NOD mice (at the age of 24 weeks) was not significantly different from that of untreated control NOD mice. However, the streptozotocin-treated animals showed significantly lower pancreatic insulin content than the control mice. These results show that an anti-Beta cell autoimmune process in NOD mice has a predisposing effect on the induction of diabetes by a sub-diabetogenic dose of streptozotocin, and suggest that the precipitation of clinical diabetes by some environmental insults in subjects with pre-existing pre-clinical autoimmune Beta-cell destruction may be one mechanism of disease presentation in human Type 1 (insulin-dependent) diabetes.

Initial role of macrophage in the development of anti-beta-cell cellular autoimmunity in multiple low-dose streptozotocin-induced diabetes in mice

Multiple injections of low doses of streptozotocin to susceptible strains of mice produce an experimental autoimmune diabetes mellitus. To investigate the possible initial role of macrophages in the development of insulitis, we studied the effect of macrophage-toxic silica administration on the development of in vitro cellular cytotoxic immune response against pancreatic beta-cells. Multiple streptozotocin-treated mice developed hyperglycemia at day 12 and their splenocytes showed cytotoxicity against cultured rat insulinoma cells. Mice given silica and streptozotocin together remained normoglycemic and their splenocytes showed no cytotoxicity. In contrast, in vitro depletion of macrophages from the splenocytes of mice given multiple streptozotocin alone did not abolish the cytotoxicity. These results show that macrophages themselves contribute little to the cellular cytotoxicity, but are necessary for the development of cytotoxic cells. From these results we suggest that there are at least two different steps in the development of insulitis; the presentation of beta-cell autoantigen by macrophages to helper-T cells, followed by the development of beta-cell-specific cytotoxic cells.

Microcystic adenomas of the pancreas. Report of three cases with two of multicentric origin

Three cases of microcystic adenomas of the pancreas with special reference to multicentric origin are described. The gross features and light microscopic findings were consistent with those described as being microcystic adenomas, but in two cases the gross examination and gelatin-embedded giant slices revealed multiple, isolated development of tumors ranging from submacroscopic nodules to tumors 4.5 cm in diameter. The larger tumors often showed ragged margins with small satellite nodules around the masses. A central fibrolamellar stellate core with centrifugally radiating septation was found in most of the tumor masses, even in the smaller ones. Ultrastructural and immunohistochemical findings revealed a single row of glycogen-rich epithelial cells, but participation of myoepithelial cells was not confirmed. Instead, vimentin-positive cells (pericytes) within the interstitial space incorporated closely with the basal lamina of the cyst wall. This study suggests that a small percentage of microcystic adenomas of the pancreas develop in multiple tumors, and some appear as a single tumor by their confluence.

Hyperglycemia per se can reduce plasma free fatty acid and glycerol levels in the acutely insulin-deficient dog

To evaluate the in vivo effect of hyperglycemia per se on plasma free fatty acid (FFA) and glycerol concentrations, euglycemic and hyperglycemic clamp studies were performed in six overnight fasted dogs in the state of insulin deficiency produced by somatostatin (SRIF) infusion. The mean blood glucose concentrations during the steady-state (the second hour of each study) averaged 4.65 +/- 0.10 mmol/L in euglycemic clamp and 14.11 +/- 0.10 mmol/L in hyperglycemic clamp. During the SRIF infusion, plasma FFA concentrations increased from 0.32 +/- 0.05 mumol/mL at the basal state to 0.76 +/- 0.04 mumol/mL at the steady-state in euglycemic clamp and from 0.26 +/- 0.04 mumol/mL to 0.43 +/- 0.02 mumol/mL in hyperglycemic clamp. Plasma glycerol concentrations increased from the basal value of 0.07 +/- 0.01 mumol/mL to 0.15 +/- 0.01 mumol/mL during the steady-state in euglycemic clamp and from 0.06 +/- 0.01 mumol/mL to 0.08 +/- 0.01 mumol/mL in hyperglycemic clamp. The steady-state concentrations of plasma FFA and glycerol in hyperglycemic clamp were significantly lower than those in euglycemic clamp (P less than .001; respectively). These results suggest that hyperglycemia per se might decrease plasma FFA and glycerol concentrations at least in part by decreasing lipolysis in the acutely insulin-deficient dog.

Preferential infiltration of macrophages during early stages of insulitis in diabetes-prone BB rats

The subpopulation of lymphoid cells at the different stages of insulitis in BB rats was determined by immunohistochemical techniques with various monoclonal antibodies, including the recently developed OX41, which distinguishes macrophages from T-lymphocytes, OX19 for pan-T-lymphocytes, W3/25 for both helper T-lymphocytes and macrophages, OX8 for cytotoxic T-lymphocytes and natural killer cells, and OX12 for B-lymphocytes. The major population of infiltrated cells found during the early stages of insulitis appeared to be macrophages. This preceded invasion by a mixed population of cells, including both T- and B-lymphocytes and/or natural killer cells. The preferential infiltration of macrophages during the early stages of insulitis strongly suggested that there might be an initial change in the target beta-cells that precedes their immune destruction, although the amplification of immune response by activated T-lymphocytes and natural killer cells at a later stage seemed to be required for the clinical expression of the disease.

Evidence for initial involvement of macrophage in development of insulitis in NOD mice

Macrophages have been shown to be the major population of infiltrated immunocytes at the early stage of insulitis in diabetes-prone BB rats. This study was undertaken to investigate the role of macrophages in the development of insulitis in nonobese diabetic (NOD) mice. Administration of cyclophosphamide to NOD mice resulted in a significant increase in the incidence of overt diabetes and severity of insulitis compared with that in untreated NOD mice. Intraperitoneal injections of silica completely prevented the development of diabetes and insulitis in both cyclophosphamide-treated and untreated animals. Because silica is selectively toxic to macrophages, the results suggest that macrophages play an important role in the initiation of insulitis in NOD mice.

Prevention of lymphocytic thyroiditis and insulitis in diabetes-prone BB rats by the depletion of macrophages

Diabetes-prone biobreeding (BB) rats often develop lymphocytic thyroiditis. Intraperitoneal administration of silica to young BB rats (40-days-old) nearly completely prevented the development of lymphocytic thyroiditis as well as insulitis. Since silica is known to be toxic to macrophages, these data suggest that the presentation of autoantigen(s) on the specific target cells such as thyroid and pancreatic B cells by antigen-presenting cells (e.g., macrophages) would be the initial step in the development of organ-specific autoimmune diseases in diabetes-prone BB rats.

Artificial induction of intravascular lipolysis by lipid-heparin infusion leads to insulin resistance in man

Although extensive evidence indicates that free fatty acids can decrease glucose utilization in vitro, it is still controversial how an increase in lipolysis affects glucose metabolism in man. To test the hypothesis that an increase in lipolysis is related to insulin resistance, we examined the effect of lipid-heparin infusion on glucose metabolism in ten normal subjects by the euglycaemic glucose clamp technique and isotopic determination of glucose turnover. In the control euglycaemic clamp studies with insulin infusion at 0.2 and 1.0 mU.kg-1.min-1, endogenous glucose production was suppressed from the basal rate of 2.0 +/- 0.3 mg.kg-1min-1 to 1.1 +/- 0.7 mg.kg-1.min-1 and -0.4 +/- 0.7 mg.kg-1min-1 respectively. Glucose utilization increased from the basal rate of 2.0 +/- 0.3 mg.kg-1min-1 to 2.3 +/- 0.5 mg.kg-1min-1 and 5.9 +/- 1.8 mg.kg-1min-1 respectively. When the euglycaemic clamp studies were coupled with lipid-heparin infusion at comparable low and high rates of insulin infusion, endogenous glucose production increased (1.8 +/- 0.7 mg.kg-1.min-1, p less than 0.001, and 0.3 +/- 0.6 mg.kg-1.min-1, p less than 0.05, respectively), and glucose utilization decreased (2.1 +/- 0.3 mg.kg-1.min-1, not significant, and 3.2 +/- 0.7 mg.kg-1.min-1, p less than 0.001 respectively). These data suggest that the artificial induction of intravascular lipolysis by lipid-heparin infusion leads to a state of insulin resistance in man.

Effects of several simple sugars on serum glucose and serum fructose levels in normal and diabetic subjects

Fructose has a reaction constant 7.5 times as high as that of glucose in its nonenzymatic reaction with protein in vitro. The effects of glucose, sucrose and fructose ingestion on serum fructose and glucose levels were studied to evaluate the overall biohazard, i.e., the probability of their altering proteins while circulating in the blood. Normal and diabetic subjects were given either 75 g glucose, 75 g fructose, 75 g sucrose, or 112.5 g fructose after fasting, and their serum levels of sugars were measured at 0, 1, 2 and 3 h. In normal subjects, fructose ingestion produced significantly lower serum glucose levels and significantly higher serum fructose levels than did glucose ingestion, while sucrose produced intermediate results. The glycemic effect was found to be lowest for fructose and highest for glucose. The calculated overall biohazard was, however, highest for fructose and lowest for glucose in normal subjects. Furthermore, the serum fructosemic index was directly proportional to the amount of fructose ingested. In diabetic subjects, blood fructose clearance was significantly more delayed than in the controls when the same amount of fructose was ingested. These results suggest that an evaluation of the effects of simple in the diabetic diet requires a closer examination of the overall biological effects of the sugars.