Ten-year hip fracture incidence rate trends in a large California population, 1997-2006.

UNLABELLED: Hip fractures are a large public health problem with significant negative impact on an individual's overall health and survival. But while the total numbers of persons affected by hip fractures may be anticipated to increase, incidence rates appear to be declining. INTRODUCTION: To describe annual hip fracture incidence rate trends in an integrated health-care organization over 1997-2006, during which a proactive bone health program was initiated program-wide and other secular trends occurred in the population. METHODS: For this ecologic trend study, we identified all men and women ≥45 years old as of January 1 of each year. Incident fractures for each year were identified using ICD-9 diagnosis codes 820-820.9, excluding all subjects who had fractures in prior years. Annual person-time at risk for hip fracture was determined from enrollment data. Sex- and age-specific and adjusted annual incidence rates were calculated. RESULTS: The overall annual hip fracture incidence rate for men declined from 1.52/1,000 person-years in 1997 to 1.29/1,000 person-years in 2006, a 15.3% (95% confidence interval [CI]=6.2-24.5) decrease. For women, incidence declined from 2.65/1,000 person-years in 1997 to 2.24/1,000 person-years in 2006, a 15.3% (95% CI=8.7-21.9) decrease. Among subjects aged 85 years or older, incidence rates for men declined from 27.0/1,000 to 18.9/1,000 person-years, and for women they declined from 32.7/1,000 to 27.1/1,000 person-years. CONCLUSION: Hip fracture incidence has been declining in all age groups over the past 10 years. While many factors may contribute to this decline, the results are consistent with a potential benefit of the active bone health intervention.

Common variants in genes encoding adiponectin (ADIPOQ) and its receptors (ADIPOR1/2), adiponectin concentrations, and diabetes incidence in the Diabetes Prevention Program.

AIMS: Baseline adiponectin concentrations predict incident Type 2 diabetes mellitus in the Diabetes Prevention Program. We tested the hypothesis that common variants in the genes encoding adiponectin (ADIPOQ) and its receptors (ADIPOR1, ADIPOR2) would associate with circulating adiponectin concentrations and/or with diabetes incidence in the Diabetes Prevention Program population. METHODS: Seventy-seven tagging single-nucleotide polymorphisms (SNPs) in ADIPOQ (24), ADIPOR1 (22) and ADIPOR2 (31) were genotyped. Associations of SNPs with baseline adiponectin concentrations were evaluated using linear modelling. Associations of SNPs with diabetes incidence were evaluated using Cox proportional hazards modelling. RESULTS: Thirteen of 24 ADIPOQ SNPs were significantly associated with baseline adiponectin concentrations. Multivariable analysis including these 13 SNPs revealed strong independent contributions of rs17366568, rs1648707, rs17373414 and rs1403696 with adiponectin concentrations. However, no ADIPOQ SNPs were directly associated with diabetes incidence. Two ADIPOR1 SNPs (rs1342387 and rs12733285) were associated with ∼18% increased diabetes incidence for carriers of the minor allele without differences across treatment groups, and without any relationship with adiponectin concentrations. CONCLUSIONS: ADIPOQ SNPs are significantly associated with adiponectin concentrations in the Diabetes Prevention Program cohort. This observation extends prior observations from unselected populations of European descent into a broader multi-ethnic population, and confirms the relevance of these variants in an obese/dysglycaemic population. Despite the robust relationship between adiponectin concentrations and diabetes risk in this cohort, variants in ADIPOQ that relate to adiponectin concentrations do not relate to diabetes risk in this population. ADIPOR1 variants exerted significant effects on diabetes risk distinct from any effect of adiponectin concentrations.

Enhanced expression of PAI-1 in visceral fat: possible contributor to vascular disease in obesity.

The presence of obesity increases the risk of thrombotic vascular diseases. The role of fat accumulation and its effect on plasminogen activator inhibitor-1 (PAI-1) levels was investigated in humans and animals. Plasma PAI-1 levels were closely correlated with visceral fat area but not with subcutaneous fat area in human subjects. PAI-1 mRNA was detected in both types of fat tissue in obese rats but increased only in visceral fat during the development of obesity. These data suggest that an enhanced expression of the PAI-1 gene in visceral fat may increase plasma levels and may have a role in the development of vascular disease in visceral obesity.

Insulin-mediated regulation of decidual protein induced by progesterone (DEPP) in adipose tissue and liver.

We analyzed the profile of the genes expressed in human adipose tissue and identified the fat-derived molecules, adiponectin and aquaporin 7, which modulate glucose and lipid metabolism. The same Bodymap analysis revealed abundant expression of the decidual protein induced by progesterone (DEPP) in the white adipose tissue. Northern blot analysis confirmed that human DEPP mRNA was highly expressed in white adipose tissue. Mouse DEPP mRNA was detected in heart, lung, skeletal muscle, and white adipose tissue under feeding state. In contrast, under fasting state, mouse DEPP mRNA was enhanced in lung, skeletal muscle, and white adipose tissue and it appeared also in the liver and kidney, suggesting up regulation of DEPP by fasting. Because fasting-induced DEPP expression was observed in insulin-sensitive organs, we investigated the regulation of DEPP in white adipose tissue and liver. During adipogenesis of mouse 3T3-L1 cells, DEPP mRNA increased in a differentiation-dependent manner similar to adiponectin and aquaporin 7. Treatment of cultured 3T3-L1 mature adipocytes, rat H4IIE, and human HepG2 hepatoma cells with insulin significantly decreased DEPP mRNA levels in dose- and time-dependent manners. IN VIVO experiments showed significant decrease of hepatic and adipose DEPP mRNA levels in refed mice, compared to fasted animals, and also showed significant increase in DEPP mRNA in streptozotocin-induced insulin-deficient diabetic mice. These results indicate that DEPP is a novel insulin-regulatory molecule expressed abundantly in insulin-sensitive tissues including white adipose tissue and liver.

mRNA concentrations of MIF in subcutaneous abdominal adipose cells are associated with adipocyte size and insulin action.

OBJECTIVE: To determine whether the mRNA concentrations of inflammation response genes in isolated adipocytes and in cultured preadipocytes are related to adipocyte size and in vivo insulin action in obese individuals. DESIGN: Cross-sectional inpatient study. SUBJECTS: Obese Pima Indians with normal glucose tolerance. MEASUREMENTS: Adipocyte diameter (by microscope technique; n=29), expression of candidate genes (by quantitative real-time PCR) in freshly isolated adipocytes (monocyte chemoattractant protein (MCP) 1 and MCP2, macrophage inflammatory protein (MIP) 1alpha, MIP1beta and MIP2, macrophage migration inhibitory factor (MIF), tumor necrosis factor alpha, interleukin (IL) 6 and IL8; n=22) and cultured preadipocytes (MCP1, MIP1alpha, MIF, IL6 and matrix metalloproteinase 2; n=33) from subcutaneous abdominal adipose tissue (by aspiration biopsy, n=34), body fat by dual-energy X-ray absorptiometry, glucose tolerance by 75 g oral glucose tolerance test and insulin action by euglycemic-hyperinsulinemic clamp (insulin infusion rate 40 mU m(-2) min(-1)) (all n=34). RESULTS: MIF was the only gene whose expression in both freshly isolated adipocytes and cultured preadipocytes was positively associated with adipocytes diameter and negatively associated with peripheral and hepatic insulin action (all P<0.05). In multivariate analysis, the association between adipocyte MIF mRNA concentrations and adipocytes diameter was independent of the percentage of body fat (P=0.03), whereas adipocyte MIF mRNA concentrations, but not adipocyte diameter, independently predicted peripheral insulin action. The mRNA expression concentrations of the MIF gene in adipocytes were not associated with plasma concentrations of MIF, but were negatively associated with plasma adiponectin concentrations (P=0.004). In multivariate analysis, adipocyte MIF RNA concentrations (P=0.03) but not plasma adiponectin concentrations (P=0.4) remained a significant predictor of insulin action. CONCLUSIONS: Increased expression of MIF gene in adipose cells may be an important link between obesity characterized by enlarged adipocytes and insulin resistance in normal glucose tolerant people.

Adiponectin plays a protective role in caerulein-induced acute pancreatitis in mice fed a high-fat diet.

BACKGROUND: Obesity is a risk factor for acute pancreatitis (AP), but the molecular mechanism remains unclear. Adiponectin, an adipose tissue-derived secretory factor, has anti-inflammatory properties in addition to various biological functions, and its plasma concentrations are reduced in obese subjects. However, the role of adiponectin in AP has not been investigated. AIM: To determine the effects of adiponectin on AP. METHODS: We investigated the effects of adiponectin on experimental AP by using adiponectin-knockout (APN-KO) mice and adenovirus-mediated adiponectin over-expression. AP was induced by 10 hourly intraperitoneal injections of low-dose caerulein (10 microg/kg) after 2 week feeding of normal chow or a high-fat diet (HFD) in wild-type (WT) and APN-KO mice. We evaluated the severity of AP biochemically and morphologically. RESULTS: Low-dose caerulein treatment did not induce pancreatic damage in either WT or APN-KO mice under normal chow feeding. APN-KO mice, but not WT mice, fed a HFD and then treated with caerulein developed pancreatic damage and inflammation, accompanied by increased macrophage/neutrophil infiltration and upregulation of pro-inflammatory mediators such as tumour necrosis factor alpha in the pancreas. Adenovirus-mediated over-expression of adiponectin attenuated the severity of HFD/caerulein-induced AP in APN-KO mice. CONCLUSIONS: Adiponectin plays a protective role in caerulein-induced AP in HFD-fed mice.

Impact of glycerol gateway molecule in adipocytes.

Glycerol is one of the essential nutrients in the mammalian body. Glycerol released from adipocytes is delivered to the liver and used for gluconeogenesis. The molecular mechanism of glycerol transport across the cell membrane remains unclear. AQPadipose, which we identified in human adipose cDNA project and later found to be human AQP7, is expressed in adipose tissue, and upregulated during fasting. AQP7 belongs to the aquaglyceroporin subfamily to permealize glycerol as well as water. Loss of function mutation of AQP7 in human caused disturbance of normal rise of plasma glycerol. Disruption of AQP7 gene in mice resulted in profound hypoglycemia during prolonged fasting because of impaired glycerol supply to the liver. In obesity, AQP7 is overexpressed in visceral fat,accompanied by portal hyperglycerolemia and systemic hyperglycemia. Considered together, these works indicate that AQP7 functions as a glycerol gateway molecule in adipocytes.

Stimulation of the activity and mRNA level of hepatic triacylglycerol lipase by triiodothyronine in HepG2 cells.

We have studied the effects of triiodothyronine (T3) on the production of hepatic triacylglycerol lipase (HTGL) in the human hepatocellular carcinoma cell line, HepG2, by measuring its activity and mRNA levels. The HTGL activity released into the medium by heparin, increased after the addition of T3 in a both time- (27% increase after 24 and 75% increase after 48 h) and dose-dependent manner (maximum activity with over 0.2 micrograms/ml of T3 in the medium). Messenger RNA levels of HTGL in cells incubated with T3 for 24 and 48 h were increased by 33% and 98% compared to those of the control. These results suggest that the production of HTGL may be regulated by thyroid hormone at the level of gene expression.

Extralysosomal degradation of high-density lipoproteins in a human hepatoma cell line, Mahlavu.

Lipoprotein metabolism has been investigated in a novel human hepatoma cell line, Mahlavu, which has been reported to possess the characteristics of hepatocytes. Low-density lipoprotein (LDL) was degraded by Mahlavu cells. LDL taken up by the cells suppressed intracellular cholesterol biosynthesis and promoted cholesterol esterification in a manner similar to that of HepG2 cells. High-density lipoprotein (HDL) was also degraded by Mahlavu cells, whereas it was not degraded by fibroblasts. We compared the mode of intracellular metabolism of HDL to that of LDL. In contrast to the LDL receptor pathway, the degradation of HDL was not inhibited by 100 microM chloroquine added to the medium, indicating that the degradation may not occur in lysosomes. Cholesterol taken up as HDL-cholesterol by the Mahlavu cells had no effect on the intracellular biosynthesis of cholesterol nor on cholesterol esterification. The conditioned media in which Mahlavu cells had been cultured did not promote the degradation of HDL, suggesting that HDL is degraded intracellularly. These data suggest that HDL is taken up and degraded by the liver cells in contrast to extrahepatic peripheral cells such as fibroblasts and macrophages in which the degradation of HDL does not occur. The results indicate that HDL-associated cholesterol may be processed via a pathway different from that of LDL metabolism and that the degradation of HDL occurs extralysosomally.

Marked enhancement of acyl-CoA synthetase activity and mRNA, paralleled to lipoprotein lipase mRNA, in adipose tissues of Zucker obese rats (fa/fa).

To clarify the role of acyl-CoA synthetase in development of obesity, the mRNA levels and activities were studied in Zucker fatty rats (fa/fa). In Zucker fatty rats compared with their lean littermates, marked enhancement of ACS were observed in adipose tissues. Obese/lean rats ratio of ACS activity and mRNA in abdominal subcutaneous fat (3.3- and 3.9-fold, respectively) were greater than in mesenteric fat (2.0- and 2.2-fold). The enhancement of ACS activity and mRNA in the liver of fatty rats (1.2- and 1.8-fold) were less than those in the adipose tissues. There were no enhancement of ACS activities and mRNA levels in heart tissue of the obese rats. LPL mRNA levels were also enhanced in adipose tissue of fatty rats and obese/lean ratio of LPL mRNA was also higher in abdominal subcutaneous fat than mesenteric fat (6.2- vs 3.1-fold). The larger obese/lean rats ratio of LPL and ACS parameters in abdominal subcutaneous fat than mesenteric fat may be related to the observation that the increase of subcutaneous fat weight was larger than that of mesenteric fat weight in fatty rats (21.1- vs 4.9-fold). Integrated enhancement of LPL and ACS gene expression in adipose tissue may play an important role in the development of obesity.

Adipocyte-derived plasma protein, adiponectin, suppresses lipid accumulation and class A scavenger receptor expression in human monocyte-derived macrophages.

BACKGROUND: Excessive lipid accumulation in macrophages plays an important role in the development of atherosclerosis. Recently, we discovered an adipocyte-specific plasma protein, adiponectin, that is decreased in patients with coronary artery disease. We previously demonstrated that adiponectin acts as a modulator for proinflammatory stimuli and inhibits monocyte adhesion to endothelial cells. The present study investigated the effects of adiponectin on lipid accumulation in human monocyte-derived macrophages. METHODS AND RESULTS: Human monocytes were differentiated into macrophages by incubation in human type AB serum for 7 days, and the effects of adiponectin were investigated at different time intervals. Treatment with physiological concentrations of adiponectin reduced intracellular cholesteryl ester content, as determined using the enzymatic, fluorometric method. The adiponectin-treated macrophages contained fewer lipid droplets stained by oil red O. Adiponectin suppressed the expression of the class A macrophage scavenger receptor (MSR) at both mRNA and protein levels by Northern and immunoblot analyses, respectively, without affecting the expression of CD36, which was quantified by flow cytometry. Adiponectin reduced the class A MSR promoter activity, as measured by luciferase reporter assay. Adiponectin treatment dose-dependently decreased class A MSR ligand binding and uptake activities. The mRNA level of lipoprotein lipase as a marker of macrophage differentiation was decreased by adiponectin treatment, but that of apolipoprotein E was not altered. Adiponectin was detected around macrophages in the human injured aorta by immunohistochemistry. CONCLUSIONS: The adipocyte-derived plasma protein adiponectin suppressed macrophage-to-foam cell transformation, suggesting that adiponectin may act as a modulator for macrophage-to-foam cell transformation.

Adiponectin, an adipocyte-derived plasma protein, inhibits endothelial NF-kappaB signaling through a cAMP-dependent pathway.

BACKGROUND: Among the many adipocyte-derived endocrine factors, we found an adipocyte-derived plasma protein, adiponectin, that was decreased in obesity. We recently demonstrated that adiponectin inhibited tumor necrosis factor-alpha (TNF-alpha)-induced expression of endothelial adhesion molecules and that plasma adiponectin level was reduced in patients with coronary artery disease (CIRCULATION: 1999;100:2473-2476). However, the intracellular signal by which adiponectin suppressed adhesion molecule expression was not elucidated. The present study investigated the mechanism of modulation for endothelial function by adiponectin. METHODS AND RESULTS: The interaction between adiponectin and human aortic endothelial cells (HAECs) was estimated by cell ELISA using biotinylated adiponectin. HAECs were preincubated for 18 hours with 50 microg/mL of adiponectin, then exposed to TNF-alpha (10 U/mL) or vehicle for the times indicated. NF-kappaB-DNA binding activity was determined by electrophoretic mobility shift assays. TNF-alpha-inducible phosphorylation signals were detected by immunoblotting. Adiponectin specifically bound to HAECs in a saturable manner and inhibited TNF-alpha-induced mRNA expression of monocyte adhesion molecules without affecting the interaction between TNF-alpha and its receptors. Adiponectin suppressed TNF-alpha-induced IkappaB-alpha phosphorylation and subsequent NF-kappaB activation without affecting other TNF-alpha-mediated phosphorylation signals, including Jun N-terminal kinase, p38 kinase, and Akt kinase. This inhibitory effect of adiponectin is accompanied by cAMP accumulation and is blocked by either adenylate cyclase inhibitor or protein kinase A (PKA) inhibitor. CONCLUSIONS: These observations raise the possibility that adiponectin, which is naturally present in the blood stream, modulates the inflammatory response of endothelial cells through cross talk between cAMP-PKA and NF-kappaB signaling pathways.

Circulating concentrations of the adipocyte protein adiponectin are decreased in parallel with reduced insulin sensitivity during the progression to type 2 diabetes in rhesus monkeys.

Adiponectin is an adipose-specific plasma protein whose plasma concentrations are decreased in obese subjects and type 2 diabetic patients. This protein possesses putative antiatherogenic and anti-inflammatory properties. In the current study, we have analyzed the relationship between adiponectin and insulin resistance in rhesus monkeys (Macaca mulatta), which spontaneously develop obesity and which subsequently frequently progress to overt type 2 diabetes. The plasma levels of adiponectin were decreased in obese and diabetic monkeys as in humans. Prospective longitudinal studies revealed that the plasma levels of adiponectin declined at an early phase of obesity and remained decreased after the development of type 2 diabetes. Hyperinsulinemic-euglycemic clamp studies revealed that the obese monkeys with lower plasma adiponectin showed significantly lower insulin-stimulated peripheral glucose uptake (M rate). The plasma levels of adiponectin were significantly correlated to M rate (r = 0.66, P < 0.001). Longitudinally, the plasma adiponectin decreased in parallel to the progression of insulin resistance. No clear association was found between the plasma levels of adiponectin and its mRNA levels in adipose tissue. These results suggest that reduction in circulating adiponectin may be related to the development of insulin resistance.

Circulating adiponectin levels are reduced in nonobese but insulin-resistant first-degree relatives of type 2 diabetic patients.

Adiponectin, one of the most abundant gene transcript proteins in human fat cells, has been shown to improve insulin action and is also suggested to exert antiatherogenic effects. We measured circulating adiponectin levels and risk factors for atherosclerosis in 45 healthy first-degree relatives of type 2 diabetic subjects (FDR) as well as 40 healthy control subjects (CON) without a known family history of diabetes. Insulin sensitivity (S(i)) was studied with the minimal model, and measurements of adiponectin, metabolic variables, inflammatory markers, and endothelial injury markers, as well as lipoprotein concentrations, were performed. FDR were insulin resistant (3.3 +/- 2.4 vs. 4.5 +/- 2.6 x 10(-4) x min(-1) per microU/ml [mean +/- SD], P < 0.01), and their circulating plasma adiponectin levels (6.6 +/- 1.8 vs. 8.1 +/- 3.0 microg/ml, P < 0.03) were decreased. After adjustments for age in FDR, adiponectin levels were negatively correlated with fasting proinsulin (r -0.64, P < 0.001), plasminogen activator inhibitor (PAI)-1 activity (r -0.56, P < 0.001), fasting insulin (r -0.55, P < 0.001), and acute insulin response (r -0.40, P < 0.05); they were positively related to HDL cholesterol (r 0.48, P < 0.01) and S(i) (r 0.41, P < 0.01). Furthermore, when adjusted for age, waist, and S(i), adiponectin was associated with HDL cholesterol and proinsulin, which explained 51% of the variation in adiponectin in multiple regression analyses in that group. In conclusion, circulating plasma adiponectin levels were decreased in nonobese but insulin-resistant FDR and, in addition, related to several facets of the insulin resistance syndrome (IRS). Thus, hypoadiponectinemia may be an important component of the association between cardiovascular disease and IRS.

PPARgamma ligands increase expression and plasma concentrations of adiponectin, an adipose-derived protein.

Insulin resistance and its dreaded consequence, type 2 diabetes, are major causes of atherosclerosis. Adiponectin is an adipose-specific plasma protein that possesses anti-atherogenic properties, such as the suppression of adhesion molecule expression in vascular endothelial cells and cytokine production from macrophages. Plasma adiponectin concentrations are decreased in obese and type 2 diabetic subjects with insulin resistance. A regimen that normalizes or increases the plasma adiponectin might prevent atherosclerosis in patients with insulin resistance. In this study, we demonstrate the inducing effects of thiazolidinediones (TZDs), which are synthetic PPARgamma ligands, on the expression and secretion of adiponectin in humans and rodents in vivo and in vitro. The administration of TZDs significantly increased the plasma adiponectin concentrations in insulin resistant humans and rodents without affecting their body weight. Adiponectin mRNA expression was normalized or increased by TZDs in the adipose tissues of obese mice. In cultured 3T3-L1 adipocytes, TZD derivatives enhanced the mRNA expression and secretion of adiponectin in a dose- and time-dependent manner. Furthermore, these effects were mediated through the activation of the promoter by the TZDs. On the other hand, TNF-alpha, which is produced more in an insulin-resistant condition, dose-dependently reduced the expression of adiponectin in adipocytes by suppressing its promoter activity. TZDs restored this inhibitory effect by TNF-alpha. TZDs might prevent atherosclerotic vascular disease in insulin-resistant patients by inducing the production of adiponectin through direct effect on its promoter and antagonizing the effect of TNF-alpha on the adiponectin promoter.

Visceral fat is a major contributor for multiple risk factor clustering in Japanese men with impaired glucose tolerance.

OBJECTIVE: The significance of abdominal visceral fat accumulation was evaluated in Japanese men with impaired glucose tolerance (IGT). RESEARCH DESIGN AND METHODS: The IGT subjects (n = 123) were aged 55 +/- 9 years with a BMI of 24 +/- 3 kg/m(2). The 148 control subjects with normal glucose tolerance (NGT) were matched for age and BMI. IGT and NGT were classified according to the 1985 World Health Organization criteria. Abdominal fat distribution was analyzed by computed tomography at umbilical level. Plasma lipid, glucose, and insulin concentrations and blood pressure (BP) were measured. RESULTS: In subjects with IGT, the average visceral fat area (VFA) was significantly greater than in subjects with NGT. Fasting insulin, the sum of insulin concentrations during an oral glucose tolerance test, insulin resistance according to a homeostasis model assessment for insulin resistance (HOMA-IR), systolic BP, and serum triglyceride were significantly higher, whereas the DeltaI(30-0)/DeltaG(30-0) was significantly lower, in subjects with IGT. Subjects with IGT and NGT were then divided into three subgroups according to the number of risk factors they possessed (dyslipidemia, hypertension, neither, or both). In both IGT and NGT subjects, BMI, VFA, subcutaneous fat area, fasting insulin, HOMA-IR, and insulin secretion of the homeostasis model assessment were significantly higher in the double-risk factor subgroup than in the no-risk factor subgroup, and VFA was a potent and independent variable in association with the presence of a double risk factor. CONCLUSIONS: Visceral fat accumulation is a major contributor for multiple risk factor clustering in Japanese men with IGT and NGT.

Hepatic expression of the catalytic subunit of the apolipoprotein B mRNA editing enzyme (apobec-1) ameliorates hypercholesterolemia in LDL receptor-deficient rabbits.

Apolipoprotein (apo) B48, a protein contained in intestinally derived lipoprotein particles, is synthesized by post-transcriptional editing of apoB100 mRNA. This reaction is mediated by an enzyme complex that includes the catalytic subunit, apobec-1. The liver of most mammals, by contrast, contains only unedited apoB mRNA and secretes apoB100, the major protein component of plasma low-density lipoprotein (LDL). Because rabbits, like humans, fail to edit hepatic apoB100 mRNA, we introduced a recombinant adenovirus encoding apobec-1 into the livers of LDL receptor-defective rabbits to determine the impact on lipoprotein metabolism of hepatic apoB48 secretion. Transgene expression was mainly confined to the liver and was sustained for up to 3 weeks following virus administration, as evidenced by the presence of apobec-1 mRNA and the ability of hepatic S100 extracts to edit a synthetic apoB RNA template in vitro. The transient induction of hepatic apoB mRNA editing accompanied alterations in very-low-density lipoprotein (VLDL) size, the presence of apoB48 in fractions spanning the VLDL and LDL range, and modest reductions in total plasma cholesterol levels.

Hypoadiponectinemia in obesity and type 2 diabetes: close association with insulin resistance and hyperinsulinemia.

Plasma concentrations of adiponectin, a novel adipose-specific protein with putative antiatherogenic and antiinflammatory effects, were found to be decreased in Japanese individuals with obesity, type 2 diabetes, and cardiovascular disease, conditions commonly associated with insulin resistance and hyperinsulinemia. To further characterize the relationship between adiponectinemia and adiposity, insulin sensitivity, insulinemia, and glucose tolerance, we measured plasma adiponectin concentrations, body composition (dual-energy x-ray absorptiometry), insulin sensitivity (M, hyperinsulinemic clamp), and glucose tolerance (75-g oral glucose tolerance test) in 23 Caucasians and 121 Pima Indians, a population with a high propensity for obesity and type 2 diabetes. Plasma adiponectin concentration was negatively correlated with percent body fat (r = -0.43), waist-to-thigh ratio (r = -0.46), fasting plasma insulin concentration (r = -0.63), and 2-h glucose concentration (r = -0.38), and positively correlated with M (r = 0.59) (all P < 0.001); all relations were evident in both ethnic groups. In a multivariate analysis, fasting plasma insulin concentration, M, and waist-to-thigh ratio, but not percent body fat or 2-h glucose concentration, were significant independent determinates of adiponectinemia, explaining 47% of the variance (r(2) = 0.47). Differences in adiponectinemia between Pima Indians and Caucasians (7.2 +/- 2.6 vs. 10.2 +/- 4.3 microg/ml, P < 0.0001) and between Pima Indians with normal, impaired, and diabetic glucose tolerance (7.5 +/- 2.7, 6.1 +/- 2.0, 5.5 +/- 1.6 microg/ml, P < 0.0001) remained significant after adjustment for adiposity, but not after additional adjustment for M or fasting insulin concentration. These results confirm that obesity and type 2 diabetes are associated with low plasma adiponectin concentrations in different ethnic groups and indicate that the degree of hypoadiponectinemia is more closely related to the degree of insulin resistance and hyperinsulinemia than to the degree of adiposity and glucose intolerance.

Marked hypocholesterolemia in a case with adrenal adenoma--enhanced catabolism of low density lipoprotein (LDL) via the LDL receptors of tumor cells.

A 16-yr-old girl was hospitalized because of amenorrhea and virilism, and was diagnosed with an adrenal tumor on the right side. Her serum androgen levels were markedly elevated, and severe hypocholesterolemia (total cholesterol, 0.59 mmol/L) was observed. After resection of the tumor, her serum cholesterol level dramatically rose to normal, suggesting a role of this tumor in her marked hypocholesterolemia. To investigate the mechanism of hypocholesterolemia in this case, we examined the effects of dehydroepiandrosterone and dehydroepiandrosterone sulfate on the low density lipoprotein (LDL) receptor activity of fibroblasts. These hormones did not have any effect on LDL receptor activity. Northern blot analysis demonstrated that the LDL receptor messenger ribonucleic acid level of this tumor tissue was increased about 8-fold compared with that of normal adrenal cortex. The LDL receptor activity of the cultured cells established from this tumor was 2-fold higher than that of Hep G2 cells. Furthermore, the LDL receptor activity could not be down-regulated by an excessive dose of 25-hydroxycholesterol. These results suggest that increased LDL receptor activity and unrestricted uptake of LDL by the adrenal tumor may have caused the marked hypocholesterolemia in this patient.

Weight reduction increases plasma levels of an adipose-derived anti-inflammatory protein, adiponectin.

Adiponectin, an adipose tissue-specific plasma protein, was recently revealed to have anti-inflammatory effects on the cellular components of vascular wall. Its plasma levels were significantly lower in men than in women and lower in human subjects with obesity, type 2 diabetes mellitus, or coronary artery disease. Therefore, it may provide a biological link between obesity and obesity-related disorders such as atherosclerosis, against which it may confer protection. In this study, we observed the changes of plasma adiponectin levels with body weight reduction among 22 obese patients who received gastric partition surgery. A 46% increase of mean plasma adiponectin level was accompanied by a 21% reduction in mean body mass index. The change in plasma adiponectin levels was significantly correlated with the changes in body mass index (r = -0.5, P = 0.01), waist (r = -0.4, P = 0.04) and hip (r = -0.6, P = 0.0007) circumferences, and steady state plasma glucose levels (r = -0.5, P = 0.04). In multivariate linear regression models, the increase in adiponectin as a dependent variable was significantly related to the decrease in hip circumference (beta = -0.16, P = 0.028), after adjusting body mass index and waist circumference. The change in steady state plasma glucose levels as a dependent variable was related to the increase of adiponectin with a marginal significance (beta = -0.92, P = 0.053), after adjusting body mass index and waist and hip circumferences. In conclusion, body weight reduction increased the plasma levels of a protective adipocytokine, adiponectin. In addition, the increase in plasma adiponectin despite the reduction of the only tissue of its own synthesis suggests that the expression of adiponectin is under feedback inhibition in obesity.