Endocrine pancreatic cells of postatal “diabetes” (DB) mice in cell culture

Summary Ultrastructural characteristics as well as secretory and biosynthetic behavior of monolayer pancreatic cell cultures established from 4-day-old C57BL/KsJ misty diabetic (m db/ m db) mice have been studied in comparison to normal littermate controls. Hypersecretion of glucagon by α-cells from BL/Ks misty diabetic mice after 2 days in vitro was found to precede any hyperfunction of the insulin-secreting β-cells. The increased level of glucagon-release in BL/Ks cell cultures from diabetic mice was accompanied by a greatly enhanced level of incorporation of [³H] tryptophan into glucagon-like molecules whose specific radioactivity was up to 15-fold higher than that observed in cultures from genetic controls. The finding of an α-cell dysfunction in cultures established from preweaning diabetic BL/Ks mice suggests that glucagon could play an early role in shaping the events that culminate in the expression of frank diabetes in this inbred strain. This study was supported in part by NIH Grants AM 17631 and AM 14461, and a grant from the Juvenile Diabetes Foundation. The Jackson Laboratory is fully accredited by the American Association for Accrediation of Laboratory Animal Care.     

Expression of the db (diabetes) gene in mice with hereditary load by generalized autoimmune pathology]

A model of genetically determinate diabetes mellitus in hybrid db/db mice with hereditary load by generalized autoimmune pathology has been described. The data on the character of hormonal-metabolic disturbances permit a conclusion on more serious course of diabetes mellitus in mice (C57Bl/Ks x NZB)F2 db/db as against (C57BL/Ks x NZW)F2 db/db, that is correlated with expression of autoimmune pathology in parent lines of New Zealand mice NZB and NZW. It is stated that diabetic syndrome in males proceeds in more serious form than in females.     

Metabolic responses to leptin in obese db/db mice are strain dependent

Obese, diabetic C57BL/Ks db/db mice that lack the long-form leptin receptor exhibit no decrease in body weight or food intake when treated with leptin. Here we compared responses to leptin in two strains of db/db mice: C57BL/6J mice that are hyperglycemic and hyperinsulinemic and C57BL/Ks that are hyperglycemic and normo- or hypoinsulinemic. Chronic intraperitoneal infusion of 10 microgram leptin/day partially reversed hyperglycemia in C57BL/6J male mice but exaggerated the diabetic state of female mice. Bolus intraperitoneal injections of 40 microgram leptin/day did not effect glucose in either strain of male db/db mice, whereas chronic intraperitoneal infusion of 20 microgram leptin/day significantly reduced fasting blood glucose in male mice from both strains, especially C57BL/6J mice. Food intake, body weight, rectal temperature, and body fat did not change. Chronic intraperitoneal infusion of 10 microgram leptin/day significantly reduced body fat in lean db/+ C57BL/6J but not in C57BL/Ks mice. Thus peripherally administered leptin is active in mice that have only short-form leptin receptors, and the response is dependent on the method of leptin administration and the background strain.     

Increased concentrations of basement membrane collagen fragment in urine of diabetic mice

Levels of a urinary component of basement membrane collagen (type IV) were compared in diabetic (db/db) and normal (db/+) C57BL/Ks inbred mice. A modification of the enzyme-linked immunosorbent assay (ELISA) technique was used with antigen and antibody preparations previously defined to be specific for a fragment from human basement membrane collagen. Significantly elevated levels of basement membrane collagen were found in the urine of homozygous diabetic (db/db) mice as soon as the fourth week after birth. These levels were consistently higher than those found in age-matched normal (db/+) mice throughout the 28 weeks in which measurements were made. Results described here support previous evidence that increased basement membrane collagen synthesis occurs in the db/db model of diabetic nephropathy.     

Impairment of cell-mediated immunity in mutation diabetic mice (db/db).

Mutation diabetes in the mouse occurs in the C57BL/Ks strain. All homozygous animals (db/db) develop obesity, elevated blood sugar levels and increased or normal blood insulin concentration. The defects in cellular immunity in db/db mice and their littermate controls were examined both in vivo and in vitro. Significant suppression of delayed footpad swelling and first and second set skin allograft rejection time were observed. In addition, DNA synthesis in spleen cells after nonspecific mitogen stimulation was markedly inhibited. Diabetic animals with a mean blood sugar of 512 +/- 101 mg/100 ml did not respond to exogenous insulin therapy by lowering their blood sugar levels or reversing the defect in DNA synthesis. Adding insulin to spleen cell culture in vitro had no demonstrable effect on their response to mitogens. Thus, mutation diabetic mice with their known defect in the peripheral utilization of insulin have markedly suppressed cell-mediated immune mechanisms.     

Genistein and daidzein modulate hepatic glucose and lipid regulating enzyme activities in C57BL/KsJ-db/db mice

This study examines whether anti-diabetic effects of genistein and daidzein are mediated by hepatic glucose and lipid regulating enzyme activities in type 2 diabetic animals. Male C57BL/KsJ-lepr(db)/lepr(db) (db/db) mice and age-matched non-diabetic littermates (db/+) were used in this study. The db/db mice were divided into control, genistein (0.02%, w/w) and daidzein (0.02%, w/w) groups. The blood glucose and HbA(1c) levels were significantly lower in the genistein and daidzein groups than in the control group, while glucose tolerance only was significantly improved in the genistein-supplemented group. The plasma insulin and C-peptide levels did not differ significantly between groups, yet the glucagon level was lower in the genistein and daidzein groups compared to that in the control db/db or db/+ group. The genistein and daidzein supplements increased the insulin/glucagon ratio in the type 2 diabetic animals. While the hepatic glucokinase activity was significantly lower in the db/db control group, the glucose-6-phosphatase and phosphoenolpyruvate carboxykinase activities were significantly higher in the control group compared to the db/+ group. Interestingly, these hepatic glucose metabolizing enzyme activities were reversed by the genistein and daidzein supplementation in db/db mice compared to the control group. The hepatic fatty acid synthase, beta-oxidation and carnitine palmitoyltransferase activities were all significantly lower in the genistein and daidzein groups than in the control group. The genistein and daidzein supplements also improved the plasma total cholesterol, triglyceride, HDL-cholesterol/total cholesterol, free fatty acid and hepatic triglyceride concentrations in the db/db mice. These results suggest that genistein and daidzein exert anti-diabetic effect in type 2 diabetic conditions by enhancing the glucose and lipid metabolism.     

C-Fos在db/db自发性糖尿病小鼠颌下腺的表达

目的观察转基因糖尿病小鼠下颌下腺形态学改变与原癌基因C-fos蛋白表达的关系,为糖尿病的临床及基础研究提供依据。方法引进日本C57BL/ksj-db/ m表型正常隐性基因小鼠,其近亲交配所得纯合子后代,即为db/db(单基因遗传自然发病型)糖尿病小鼠。取3、4、6、8、10月龄db/db糖尿病小鼠及相应月龄的db/ m正常小鼠下颌下腺,行HE染色及SP免疫组化染色后进行图象分析,统计各组下颌下腺C-fos阳性表达的细胞数,观察其形态学改变。结果糖尿病小鼠下颌下腺腺泡萎缩,细胞缩小,形态不规则,排列不整齐。各月龄糖尿病小鼠颌下腺C-Fos阳性细胞明显低于相应对照组(P<0.01),且逐渐减少,呈下降趋势。结论db/db糖尿病状态下颌下腺细胞表达C-Fos蛋白明显降低,c-fos低表达可能与下颌下腺实质细胞的增殖减弱性形态学变化密切相关。     

Dehydroepiandrosterone decreases elevated hepatic glucose production in C57BL/KsJ-db/db mice

Dehydroepiandrosterone (DHEA) is known to improve hyperglycemia in diabetic db/db mice that are obese and insulin resistant. In a previous study, we reported that DHEA suppresses the elevated hepatic gluconeogenic glucose-6-phosphatase (G6Pase) activity and gene expression in C57BL/KsJ-db/db mice. In the present study, we evaluated the total amount of gluconeogenesis using NaH[(14)C]CO(3) and hepatic glucose production using fructose as a substrate in primary cultured hepatocytes. Despite hyperinsulinemia, the glucose production of db/db mice in the total body and hepatocytes was elevated as compared to their heterozygote littermate C57BL/KsJ-db/+m mice. Administration of DHEA significantly decreased the blood glucose level and increased the plasma insulin level in db/db mice. Administration of DHEA decreased the elevated total body and hepatic glucose production in db/db mice. In addition, the glucose production in the primary cultured hepatocytes of db/db mice was decreased significantly by the direct addition of DHEA or DHEA-S to the medium. These results suggest that administration of DHEA suppresses the elevated total body and hepatic glucose production in db/db mice, and this effect on the liver is considered to result from increased plasma insulin and DHEA or DHEA-S itself.     

Phosphate content of muscle phosphofructokinase in the genetically diabetic mouse (C57BL/KsJ)

The amount of phosphofructokinase based on total soluble protein in extracts of skeletal muscle from genetically diabetic mice C57BL/KsJ (db/db) was about 30% lower than that of normal controls (db/m). Organic phosphate content of five control animals varied between 0.11 and 0.19 mol/mol protomer. On the other hand, the phosphate content of diabetic mice had a much broader range (0.11 to 0.39) with a mean content for five animals of 0.24 mol/mol enzyme protomer. Partial resolution of high- and low-phosphate forms can be achieved by ion-exchange chromatography. The more highly phosphorylated enzyme is slightly more sensitive to ATP inhibition than the low-phosphate enzyme.     

Coxsackievirus B infection in the mouse: Effects associated with the diabetes gene,db

Coxsackievirus B4 (CB4) replicated to equally high titers in the pancreas and other tissues of the C57BL/Ks (+/+) mouse and its genetic variants that were either heterozygous (db/+) or homozygous (db/db) for the autosomal recessive gene for diabetes, db. In contrast, the insulin-producing beta cells of both diabetic variants, but not the +/+ mice, completely degranulated during acute infection and resulted in hypoglycemia and hyperinsulemia. All db/db mice died within 13 days, with signs of severe endocrine pancreas involvement. Surviving +/+ mice maintained relatively normal glucose homeostasis. Surviving db/+ variants exhibited prolonged periods of diabetes-like disease with hypoinsulemia and abnormal glucose tolerance, even though the db gene is not phenotypically expressed in the heterozygous state.     

Hepatic glycogen metabolism in the db/db mouse

Summary Knowledge of the metabolic changes that occur in insulin-resistant type 2 diabetes is relatively lacking compared to insulin-deficient type 1 diabetes. This paper summarizes the importance of the C57BL/KsJ-db/db mouse as a model of type 2 diabetes, and illustrates the effects that insulin-deficient and insulin-resistant states have on hepatic glycogen metabolism. A longitudinal study of db/db mice of ages 2–15 weeks revealed that significant changes in certain parameters of hepatic glycogen metabolism occur during this period. The liver glycogen levels were similar between diabetic and control mice. However, glycogen particles from db/db mice were on average smaller in mass and had shorter exterior and interior chain lengths. Total phosphorylase and phosphorylase a activities were elevated in the genetically diabetic mice. This was primarily due to an increase in the amount of enzymic protein apparently the result of a decreased rate of degradation. It was not possible to find a consistent alteration in glycogen synthase activity in the db/db mice. Glycogen synthase and phosphorylase from diabetic liver revealed some changes in kinetic properties in the form of a decrease in V_max, and altered sensitivity to inhibitors like ATP. The altered glycogen structure in db/db mice may have contributed to changes in the activities and properties of glycogen synthase and phosphorylase. The exact role played by hormones (insulin and glucagon) in these changes is not clear but further studies should reveal their contributions. The db/db mouse provides a good model for type 2 diabetes and for fluctuating insulin and glucagon ratios. Its use should clarify the regulation of hepatic glycogen metabolism and other metabolic processes known to be controlled by these hormones. The other animal models of type 2 diabetes, ob/ob mouse and fatty Zucker (fa/fa) rat, show similar impairment of hepatic glycogen metabolism. The concentrations of glycogen metabolizing enzymes are high and in vitro studies indicate enhanced rate of glycogen synthesis and breakdown. However, streptozotocin-induced diabetic animals and BB rats which resemble insulin-deficient type 1 diabetes are characterized by decreased glycogen turnover as a result of reduction in the levels of glycogen metabolizing enzymes.     

Prevention of diabetic nephropathy by treatment with astaxanthin in diabetic db/db mice

Oxidative stress is implicated as an important mechanism by which diabetes causes nephropathy. Astaxanthin, which is found as a common pigment in algae, fish, and birds, is a carotenoid with significant potential for antioxidative activity. In this study, we examined whether chronic administration of astaxanthin could prevent the progression of diabetic nephropathy induced by oxidative stress in mice. We used female db/db mice, a rodent model of type 2 diabetes, and their non-diabetic db/m littermates. The mice were divided into three groups as follows: non-diabetic db/m, diabetic db/db, and diabetic db/db treated with astaxanthin. Blood glucose level, body weight, urinary albumin, and urinary 8-hydroxydeoxyguanosine (8-OHdG) were measured during the experiments. Histological and 8-OHdG immunohistochemical studies were performed for 12 weeks from the beginning of treatment. After 12 weeks of treatment, the astaxanthin-treated group showed a lower level of blood glucose compared with the non-treated db/db group; however, both groups had a significantly high level compared with the db/m mice. The relative mesangial area calculated by the mesangial area/total glomerular area ratio was significantly ameliorated in the astaxanthin-treated group compared with the non-treated db/db group. The increases in urinary albumin and 8-OHdG at 12 weeks of treatment were significantly inhibited by chronic treatment with astaxanthin. The 8-OHdG immunoreactive cells in glomeruli of non-treated db/db mice were more numerous than in the astaxanthin-treated db/db mice. In this study, treatment with astaxanthin ameliorated the progression and acceleration of diabetic nephropathy in the rodent model of type 2 diabetes. The results suggested that the antioxidative activity of astaxanthin reduced the oxidative stress on the kidneys and prevented renal cell damage. In conclusion, administration of astaxanthin might be a novel approach for the prevention of diabetes nephropathy.     

MRNA and enzyme activity of hepatic 11beta-hydroxysteroid dehydrogenase type 1 are elevated in C57BL/KsJ-db/db mice.

To evaluate the importance of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in insulin resistant diabetic C57BL/KsJ-db/db mice, we measured the activity and mRNA level of 11beta-HSD1 in the liver of db/db mice and their heterozygote litter mates, db/+m mice. The blood glucose, plasma insulin, and corticosterone levels of db/db mice were significantly higher than those of db/+m mice. Despite hyperinsulinemia, the activity level of this enzyme was significantly higher in db/db mice, and the mRNA level of hepatic 11beta-HSD1 was also significantly higher in db/db mice. Since hepatic 11beta-HSD1 in vivo mainly functions as 11-keto-reductase and does not work as 11beta-oxidase, these results suggest that the rate of hepatic conversion of 11-dehydrocorticosterone to corticosterone is increased in db/db mice, resulting in higher glucocorticoid activity in the liver. The increased hepatic corticosterone concentration due to the elevation of 11beta-HSD1 and high plasma corticosterone concentration may antagonize the action of insulin and cause insulin resistance. These findings have a potentially important implication for relationships between increased hepatic 11beta-HSD1 and insulin resistance in db/db mice. The present paper is the first to demonstrate the increased activities and mRNA level of hepatic 11beta-HSD1 in db/db mice.     

Substance P, neurokinin A, vasoactive intestinal polypeptide and gastrin releasing peptide in the intestine and pancreas of spontaneously obese-diabetic mice

The concentrations and contents of immunoreactive substance P (SP), neurokinin A (NKA), vasoactive intestinal polypeptide (VIP) and gastrin releasing peptide (GRP) were measured in acid-ethanol extracts of intestine (duodenum-jejunum-ileum) and pancreas of C57BL/KsJ diabetes-obese (db/db) mice, Aston obese-hyperglycaemic (ob/ob) mice, and their respective lean controls. The intestinal concentration of GRP and pancreatic concentrations of VIP and GRP were 36-57% lower in lean Aston mice than lean C57BL/KsJ mice, indicating the influence of genetic background in control mice. Intestinal concentrations of SP and NKA were reduced by 19-33% in the db/db and ob/ob mutants compared with their lean controls, but the intestinal contents of these peptides were normal or greater than normal due to intestinal hypertrophy of the mutant mice. The intestinal VIP concentration was not altered, but the content was increased by 87% and 25% respectively in db/db and ob/ob mice, whereas the intestinal GRP concentration was reduced by 51% in ob/ob mice. Pancreatic concentrations and contents of NKA, VIP and GRP were similar in lean and db/db C57BL/KsJ mice. However, pancreatic concentrations and contents of VIP and GRP were reduced by 51-55% in ob/ob mice compared with their lean controls. The sensitivity of the present assay did not permit accurate determination of the low pancreatic concentrations of SP. The results suggest that the spontaneous ob/ob and db/db syndromes of obesity and diabetes in mice are associated with reduced intestinal concentrations of SP and NKA. The ob/ob mouse also exhibited reductions of intestinal GRP and pancreatic GRP and VIP concentrations. These changes in regulatory peptides may relate to abnormalities of intestinal and possibly pancreatic function in obese and diabetic mutant mice.     

Antioxidative effects of Cinnamomi cassiae and Rhodiola rosea extracts in liver of diabetic mice

Both Cinnamomi cassiae and Rhodiola rosea extracts are used as anti-diabetic folk medicines. Recently, increased oxidative stress was shown to play an important role in the etiology and pathogenesis of diabetes mellitus and its complications. This study was designed to examine the effects of Cinnamomi cassiae and Rhodiola rosea extracts on blood glucose, lipid peroxidation, the level of reduced glutathione and its related enzymes (glutathione reductase, glutathione S-transferase), and the activity of the antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) in the liver of db/db mice. Diabetic C57BL/Ks db/db mice were used as experimental models. Mice were divided into control (n=10), Cinnamomi cassiae (200 mg/kg/day, n=10), and Rhodiola rosea (200 mg/kg/day, n=10) treated groups for 12 weeks of treatment. These type II diabetic mice were used to investigate the effects of Cinnamomi cassiae and Rhodiola rosea on blood glucose, reduced glutathione, glutathione reductase, glutathione S-transferase, glutathione peroxidase, lipid peroxidation, catalase and superoxide dismutase. Cinnamomi cassiae and Rhodiola rosea extracts significantly decreased on blood glucose, increased levels of reduced glutathione and the activities of glutathione reductase, glutathione S-transferase, glutathione peroxidase, catalase and superoxide dismutase in the liver. Extract treatment also significantly decreased lipid peroxidation. Cinnamomi cassiae and Rhodiola rosea extracts may be effective for correcting hyperglycemia and preventing diabetic complications.     

Reduction of diabetes-induced renal oxidative stress by a cantaloupe melon extract/gliadin biopolymers, oxykine, in mice

Oxidative stress is implicated as an important mechanism by which diabetes causes nephropathy. Oxykine is the cantaloupe melon extract rich in vegetal superoxide dismutase covered by polymeric films of wheat matrix gliadin. In this study, we examined whether chronic oral administration of oxykine could prevent the progression of diabetic nephropathy induced by oxidative stress using preclinical rodent model of type 2 diabetes. We used female db/db mice and their non-diabetic db/m littermates. The mice were divided into the following three groups: non-diabetic db/m; diabetic db/db, and diabetic db/db treated with oxykine. Blood glucose level, body weight, urinary albumin, and urinary 8-hydroxydeoxyguanosine (8-OHdG) were measured during the experiments. Histological and 8-OHdG immunohistochemical studies were preformed on 12 weeks from the beginning of treatment. After 12 weeks of treatment, the levels of blood glucose and the body weight were not significantly different between the oxykine-treated group and the non-treated db/db group, however both groups kept significantly high levels rather than db/m mice. The relative mesangial area calculated by mesangial area/total glomerular area ratio was significantly ameliorated in the oxykine treated group compared with non-treated db/db group. The increases in urinary albumin and 8-OHdG at 12 weeks of treatment were significantly inhibited by chronic treatment with oxykine. The 8-OHdG immunoreactive cells in the glomeruli of non-treated db/db mice were more numerous than that of oxykine-treated db/db mice. In this study, treatment of oxykine ameliorated the progression and acceleration of diabetic nephropathy for rodent model of type 2 diabetes. These results indicated that the oxykine reduced the diabetes-induced oxidative stress and renal mesangial cell injury. In conclusion, oxykine might be a novel approach for the prevention of diabetes nephropathy.     

Astaxanthin protects beta-cells against glucose toxicity in diabetic db/db mice

Oxidative stress induced by hyperglycemia possibly causes the dysfunction of pancreatic beta-cells and various forms of tissue damage in patients with diabetes mellitus. Astaxanthin, a carotenoid of marine microalgae, is reported as a strong anti-oxidant inhibiting lipid peroxidation and scavenging reactive oxygen species. The aim of the present study was to examine whether astaxanthin can elicit beneficial effects on the progressive destruction of pancreatic beta-cells in db/db mice--a well-known obese model of type 2 diabetes. We used diabetic C57BL/KsJ-db/db mice and db/m for the control. Astaxanthin treatment was started at 6 weeks of age and its effects were evaluated at 10, 14, and 18 weeks of age by non-fasting blood glucose levels, intraperitoneal glucose tolerance test including insulin secretion, and beta-cell histology. The non-fasting blood glucose level in db/db mice was significantly higher than that of db/m mice, and the higher level of blood glucose in db/db mice was significantly decreased after treatment with astaxanthin. The ability of islet cells to secrete insulin, as determined by the intraperitoneal glucose tolerance test, was preserved in the astaxanthin-treated group. Histology of the pancreas revealed no significant differences in the beta-cell mass between astaxanthin-treated and -untreated db/db mice. In conclusion, these results indicate that astaxanthin can exert beneficial effects in diabetes, with preservation of beta-cell function. This finding suggests that anti-oxidants may be potentially useful for reducing glucose toxicity.     

Trypanosoma brucei: infection in murine diabetes

The course of infection due to Trypanosoma brucei infection was observed in genetically diabetic and streptozotocin-induced diabetic mice. A strain of T. brucei, TREU 667, was used which produces a chronic infection in C57BL/6(B6) mice lasting greater than 60 days. Genetic diabetic mice (+db/+db) are obese, and have elevated blood glucose levels, normal levels of insulin, and impaired cell-mediated immunity. Their littermates (m+/m+, m+/+db) are of normal weight, and are normoglycemic and immunocompetent. The infected +db/+db mice lived significantly longer than the nondiabetic littermates. In contrast to this finding, streptozotocin-induced diabetic B6 mice developed higher parasitemia and had shorter survival times than control B6 mice. Continuous treatment with insulin of these streptozotocin-induced diabetic mice led to normalization of blood glucose and a significant reduction of parasitemia. While hyperglycemia may be associated with higher parasitemia and death in streptozotozin-induced diabetes, genetic factors may play an additional role in the genetic models.     

吡格列酮对db/db小鼠骨骼肌蛋白酪氨酸磷酸酶1B表达的影响

目的探讨吡格列酮对db/db小鼠骨骼肌蛋白酪氨酸磷酸酶1B（protein tyrosine phosphatase 1B,PTP1B）表达水平的影响。方法将20只4周龄db/db小鼠随机分为两组（吡格列酮组和db/db对照组）,每组10只,分别给予吡格列酮10mg/kg.d和安慰剂灌胃。另设10只同周龄db/m小鼠,给予安慰剂灌胃作为非糖尿病对照（db/m对照组）。每周监测体重、血糖,4周后用蛋白印迹法检测各组小鼠骨骼肌组织中PTP1B蛋白含量。结果db/db组小鼠骨骼肌PTP1B表达显著高于db/m组,给予吡格列酮干预,血糖、胰岛素抵抗指数显著低于db/db组（P〈0.05）,骨骼肌PTP1B表达水平亦显著降低（P〈0.05）。结论吡格列酮改善胰岛素抵抗,可能与降低骨骼肌PTP1B蛋白表达有关。     

Reduction in ABCG1 in Type 2 diabetic mice increases macrophage foam cell formation

Atherosclerosis development is accelerated severalfold in patients with Type 2 diabetes. In the initial stages of disease, monocytes transmigrate into the subendothelial space and differentiate into foam cells. Scavenger receptors and ATP binding cassette (ABC) Transporters play an important role in foam cell formation as they regulate the influx and efflux of oxidized lipids. Here, we show that peritoneal macrophages isolated from Type 2 diabetic db/db mice have decreased expression of the ABC transporter ABCG1 and increased expression of the scavenger receptor CD36. We found a 2-fold increase in accumulation of esterified cholesterol in diabetic db/db macrophages compared with wild-type control macrophages. Diabetic db/db macrophages also had impaired cholesterol efflux to high density lipoprotein but not to lipid-free apo A-I, suggesting that the increased esterified cholesterol in diabetic db/db macrophages was due to a selective loss of ABCG1-mediated efflux to high density lipoprotein. Additionally, we were able to confirm down-regulation of ABCG1 using C57BL/6J peritoneal macrophages cultured in elevated glucose in vitro (25 mM glucose for 7 days), suggesting that ABCG1 expression in diabetic macrophages is regulated by chronic exposure to elevated glucose. Diabetic KK(ay) mice were also studied and were found to have decreased ABCG1 expression without an increase in CD36. These observations demonstrate that ABCG1 plays a major role in macrophage cholesterol efflux and that decreased ABCG1 function can facilitate foam cell formation in Type 2 diabetic mice.