SHORT CHAIN FATTY ACIDS UPREGULATE ADIPOKINE PRODUCTION IN TYPE 2 DIABETES-DERIVED HUMAN ADIPOCYTES.

PURPOSE: Short chain fatty acids (SCFAs) play a major regulatory role in adipocyte function and metabolism. The aim of this study was to investigate the effects of SCFAs on adiponectin and leptin expression in adipocytes, and also to determine whether the effects of SCFA treatment in visceral adipocytes obtained from healthy subjects are different relative to the effects in adipocytes from patients with type 2 diabetes. MATERIALS AND METHODS: Human pericardiac preadipocytes and human pericardiac preadipocytes type 2 diabetes were differentiated into adipocytes for 21 days in 48-well plates. After differentiation, two kinds of mature adipocytes, human pericardiac adipocytes (HPAd) and human pericardiac adipocytes-type 2 diabetes (HPAd-T2D) were incubated with or without 1 mM of acetic acid (AA), butyrate acid (BA), and propionic acid (PA). After 48 hours of incubation, intracellular lipid accumulation was measured using oil red staining. In addition, mRNA levels of adiponectin, leptin and Peroxisome Proliferator-Activated Receptor γ (PPARγ) were determined by Real-Time PCR system. RESULTS: In HPAd, SCFA supplementation did not inhibit lipid accumulation. By contrast, both AA (p<0.01) and PA (p<0.01) significantly inhibited lipid accumulation in HPAd-T2D. Regarding mRNA levels of adiponectin, no significant changes were found in HPAd, while all three types of SCFAs significantly increased (p<0.05) adiponectin expression in HPAd-T2D. Leptin mRNA expression levels were significantly increased by treatment with all three types of SCFAs in both HPAd (p<0.05) and HPAd-T2D (p<0.05). CONCLUSION: SCFAs inhibited lipid droplet accumulation and increased mRNA expression of adiponectin and leptin in T2D-derived adipocytes.

Low serum creatinine is a type 2 diabetes risk factor in men and women: The Yuport Health Checkup Center cohort study.

AIM: Type 2 diabetes (T2D) is a risk factor for muscle loss and subsequent frailty. The reverse association, however, may also happen. This study examined whether serum creatinine level, an indicator of muscle mass, predicted diabetes development. In addition, a role for body mass index (BMI) as an effect modifier of creatinine levels was evaluated. METHODS: This cohort study included 9667 subjects without diabetes or hypertension and with normal creatinine levels at baseline. Multiple-adjusted hazard ratios (HRs) for associations between baseline creatinine and diabetes development were estimated using the Cox proportional-hazards model. Stratified analyses based on BMI were also performed. RESULTS: During the follow-up period (mean: 5.6 years), 287 (5.5%) men and 115 (2.3%) women developed T2D. HR in men with serum creatinine≤0.7mg/dL compared with 0.9-1.2mg/dL was 1.40 (95% CI: 1.05-1.87) after adjusting for age, BMI, blood pressure and fasting plasma glucose at baseline, whereas the adjusted HR in women with creatinine≤0.5mg/dL compared with 0.7-1.1mg/dL was 1.69 (95% CI: 1.04-2.76). In a subgroup analysis stratified by BMI, interactions between BMI and baseline creatinine levels for T2D were statistically significant in women with the lowest creatinine levels (P=0.08 for interaction). CONCLUSION: Low serum creatinine levels, a surrogate marker of muscle mass, predict T2D development in both genders, even after excluding the effect of diabetic and prediabetic glomerular hyperfiltration. BMI modified the association between creatinine and diabetes development in women.

Persistent fasting hyperglycaemia is more predictive of type 2 diabetes than transient fasting hyperglycaemia.

AIMS: We investigated the value of persistent fasting hyperglycaemia as assessed by repeated elevated fasting plasma glucose in predicting the progression to diabetes. METHODS: A retrospective cohort study was conducted from 1998 to 2006 inclusive among 7929 persons (37,742 person-years), with a mean age of 53.0 years at baseline. The cumulative incidence of diabetes was measured. A baseline and follow-up fasting plasma glucose were categorized as normal fasting glucose (< 5.56 mmol/l), or impaired fasting glucose (5.56-6.94 mmol/l). RESULTS: The cumulative incidence and incidence density of diabetes were 3.5% (275 cases) and 7.3 per 1000 person-years over a mean follow-up period of 4.8 years. The cumulative incidence of diabetes among subjects with impaired fasting glucose at both previous examinations (persistent impaired fasting glucose) was 30.4% (222/1518) compared with 0.6% (15/5063) of those with normal fasting glucose at both baseline and initial follow-up. The hazard ratios to develop diabetes, adjusted for possible confounders, was 37.10 (95% CI, 21.6-63.7) for persistent impaired fasting glucose versus persistent normal fasting glucose. Persistent impaired fasting glucose predicted diabetes at 80.7% (222/275) sensitivity and 83.1% (6358/7654) specificity, whereas first baseline impaired fasting glucose only predicted diabetes at 86.9% (239/275) sensitivity and 74.9% (5730/7654) specificity. The model using both previous fasting plasma glucose levels had a greater AUROC (area under receiver operating characteristic) than that using first baseline fasting plasma glucose only (0.92 vs. 0.88; P < 0.001). CONCLUSIONS: Repeated measurements of fasting plasma glucose better predicts incidence of diabetes than a single test. In particular, persistent fasting hyperglycaemia adds more substantial precision to the prediction of future diabetes than transient impaired fasting glucose. This combination is cost efficient and may be practical for early detection of high-risk individuals.

Corticotrophin-releasing factor gene transcription is directly activated after deprivation of glucocorticoids in hypothalamic cells.

Corticotrophin-releasing factor (CRF) plays a central role in controlling the hypothalamic-pituitary-adrenal axis during stressful periods. CRF neurones are activated in the hypothalamic paraventricular nucleus (PVN) in response to stress, whereas the activated CRF neurones in the PVN are suppressed by glucocorticoids. Glucocorticoids may act directly on CRF neurones because glucocorticoid receptors are expressed highly on these neurones in the PVN. CRF expression levels in the PVN are also increased by adrenalectomy in vivo. The signalling pathways involved in the control of CRF gene transcription in the hypothalamus when negative feedback by glucocorticoids after adrenalectomy is lost remain undetermined. We investigated whether CRF gene transcription is regulated by both glucocorticoids and glucocorticoid withdrawal in hypothalamic cells. The present study demonstrates that CRF gene transcription activity and mRNA levels in the hypothalamic 4B cells were not modulated by incubation with dexamethasone for a short 2-h period, although they were stimulated by incubation for longer than 5 h. CRF gene transcription activity and mRNA levels were increased after 2 h of dexamethasone deprivation. The cAMP-response element (CRE) on the promoter was the main region that is regulated by both glucocorticoids and glucocorticoid withdrawal. We observed that the intracellular cAMP production levels were transiently increased 30 min after the removal of dexamethasone, whereas they were also increased 2.5 h after incubation with dexamethasone without the removal. Phosphorylated-CRE-binding protein (CREB)/CREB protein levels were also increased rapidly after the deprivation of glucocorticoids via an adenylate cyclase pathway. Therefore, the phosphorylation of CREB contributes to the activation of CRF gene transcription after the deprivation of glucocorticoids in hypothalamic cells.

The threshold for definition of impaired fasting glucose in a Japanese population.

AIMS: We examined whether the cut-off value of fasting plasma glucose (FPG) for diagnosing impaired fasting glucose (IFG) should be lowered, using data from a large Japanese population. METHODS: A retrospective cohort study was conducted from 1998 to 2006. Follow-up (2002-2006) data were merged with baseline (1998-2002) data, yielding 11 129 persons who had participated on both occasions. Among these, 10 475 persons who did not have diabetes (known diabetes or defined as FPG > or = 7.0 mmol/l) or suspected diabetes (glycated haemoglobin > or = 6.4%) were analysed. RESULTS: During follow-up of an average of 5.4 years, 279 (5.2%) out of 5372 men and 98 (1.9%) out of 5103 women developed diabetes. According to the three baseline FPG categories (< 5.6, 5.6-6.1 and 6.2-6.9 mmol/l), 28/3401 (0.8%), 91/1456 (6.3%) and 160/515 (31.1%), respectively, in men and 13/4231 (0.3%), 30/695 (4.3%) and 55/177 (31.1%), respectively, in women developed diabetes. The optimal cut-off FPG value to predict diabetes was 5.7 mmol/l for both men (sensitivity 84.2%, specificity 76.9%) and women (81.6%, 91.0%). However, lowering the cut-off from 6.1 to 5.7 mmol/l increased the prevalence of IFG 2.7-fold in men and 3.0-fold in women. Lowering the value further to 5.6 mmol/l increased the prevalence of IFG 3.8-fold in men and 4.9-fold in women. CONCLUSIONS: It may be reasonable to retain the conventional lower FPG limit for IFG and treat FPG values of 5.6-6.1 mmol/l as non-diabetic hyperglycaemia, considering the four- to fivefold increase in individuals classified as IFG when the new cut-off is applied.

Risk factors for the progression of endoscopic Barrett's epithelium in Japan: a multivariate analysis based on the Prague C & M Criteria.

PURPOSE: To determine the prevalence and progression of Barrett's epithelium and associated risk factors in Japan. METHODS: The study population comprised 869 cases. Endoscopic Barrett's epithelium was diagnosed based on the Prague C & M Criteria. The correlations of clinical factors with the prevalence and progression of endoscopic Barrett's epithelium were examined. RESULTS: Endoscopic Barrett's epithelium was diagnosed in 374 cases (43%), in the majority of which the diagnosis was short-segment Barrett's esophagus. The progression of Barrett's epithelium was identified in 47 cases. In univariate and multiple logistic regression analyses, aging, smoking habit, and erosive esophagitis were significantly associated with the prevalence of Barrett's epithelium, whereas aging and erosive esophagitis, especially severe erosive esophagitis, were significant contributing factors to the progression of Barrett's epithelium. CONCLUSIONS: Forty-three percent of the total study population was diagnosed as having endoscopic Barrett's epithelium. During the follow-up period, 12.6% of the cases with Barrett's epithelium exhibited progression which was associated with aging and severe erosive esophagitis.

Effects of steroid pulse therapy on immunoglobulin-resistant Kawasaki disease.

BACKGROUND: The use of intravenous immunoglobulin (IVIG) is well established as an initial therapy for Kawasaki disease (KD), but treatment for IVIG-resistant KD remains uncertain AIM: To analyse the effects of intravenous methylprednisolone (IVMP) pulse therapy compared with additional IVIG in IVIG-resistant patients. METHODS: IVMP was administered to patients with KD who had persistent or recurrent fever after a single dose of IVIG, at Juntendo University Hospital and affiliated medical institutions between May 2003 and March 2006. The effectiveness of the treatment and the incidence of coronary lesions in patients who received IVMP and those who received additional IVIG were retrospectively analysed and compared by chart review. RESULTS: 411 patients with KD were treated with a single dose of IVIG. Of the 63 IVIG-resistant patients, 44 were then given IVMP and 19 were given additional IVIG. Treatment was successful in 34 (77%) of the patients who received IVMP and 12 (63%) who received additional IVIG. Five of the 10 patients who did not respond to IVMP and two of the seven who did not respond to additional IVIG developed coronary artery aneurysms. Although fever initially resolved faster in the IVMP-resistant group, there was a delay in fever recurrence, which ultimately delayed the final resolution of fever. CONCLUSIONS: The findings suggest that IVMP is an effective additional treatment for IVIG-resistant KD. However, there was a tendency for fever to recur later in IVMP-resistant patients, which could potentially delay the therapeutic decision-making process.

Fursultiamine, a vitamin B1 derivative, enhances chondroprotective effects of glucosamine hydrochloride and chondroitin sulfate in rabbit experimental osteoarthritis.

OBJECT AND DESIGN: The therapeutic effect of glucosamine hydrochloride (GH) and chondroitin sulfate (CS) in combination with fursultiamine, a vitamin B1 derivative, on the development of cartilage lesions was investigated in an animal model of osteoarthritis (OA). METHODS: The OA model was created by partial medial meniscectomy of the right knee joint (day 0). The rabbits were placed into three experimental groups: operated (OA) rabbits that received placebo treatment, OA rabbits that received GH (1000 mg/kg) + CS (800 mg/kg), and OA rabbits that received GH + CS + fursultiamine (100 mg/kg). Each treatment was initiated on day 3 and continued for 8 weeks. Macroscopic and histologic analyses were performed on the cartilage. The level of MMP-1 in OA cartilage chondrocytes was evaluated by immunohistochemistry. RESULTS: Only the group receiving combined treatment with GH + CS + fursultiamine showed a significant reduction in the severity of macroscopic and histologic lesions on tibial plateau, which is the weight bearing cartilage surface of the tibia, compared with placebo-treated OA rabbits. This treatment group also revealed a small, but significant, decrease in the body weight gain of the rabbits. In cartilage from placebo-treated OA rabbits, a significantly higher percentage of chondrocytes in superficial layer stained positive for MMP-1 compared with unoperated control. Rabbits treated with the GH + CS + fursultiamine revealed a significant reduction in the level of MMP-1. CONCLUSION: These results suggest that the chondroprotective effect of GH + CS is enhanced by the addition of fursultiamine in experimental OA. This effect was associated with a reduction in the level of MMP-1, which are known to play an important role in the pathophysiology of OA lesions.

Angiotensin-II-induced oxidative stress elicits hypoadiponectinaemia in rats.

AIMS/HYPOTHESIS: Hypertension, endothelial dysfunction and insulin resistance are associated conditions that share oxidative stress and vascular inflammation as common features. Adiponectin is an abundant plasma adipokine that plays a physiological role in modulating lipid metabolism and exerts a potent anti-inflammatory activity. We hypothesised that adiponectin levels decrease in response to oxidative stress and that this may promote the development of hypertension, endothelial dysfunction and insulin resistance. METHODS: Rats were infused with angiotensin II (AngII) or its vehicle, either alone or in combination with tempo1 (4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl), a membrane-permeable metal-independent superoxide dismutase mimetic, or tetrahydrobiopterin (BH4), one of the most potent naturally occurring reducing agents and an essential cofactor for nitric oxide synthase activity. Heart rate, systolic blood pressure, body weight and serum levels of adiponectin were measured on day 7 of treatment, and then the animals were killed. Vessel tone and superoxide production were measured ex vivo in thoracic vascular rings. The expression of adiponectin mRNA in adipose tissue was assessed by Northern blotting, and in 3T3-L1 adipocytes exposed to H2O2 by real-time PCR. The expression of NAD(P)H oxidase subunit mRNAs in the rats was assessed by RT-PCR and real-time PCR. RESULTS: Hypertension and endothelial dysfunction were induced in rats by infusion of AngII and reversed by administration of tempol. Plasma concentrations of adiponectin and adipose tissue levels of adiponectin mRNA were decreased in AngII-infused rats, and this effect was prevented by cotreatment with tempol or BH4. The production of superoxide anions (O2-) was significantly increased in the aortae of AngII-treated rats, and this increase was prevented by the administration of tempol or BH4. Levels of mRNAs that encode NAD(P)H oxidase components, including p22phox, gp91phox, p47phox and Rac1, were similarly increased in adipose tissue, aortae and hearts of AngII-infused rats. Cotreatment of rats with tempol or BH4 reversed AngII-induced increases in NAD(P)H oxidase subunit mRNAs. Fully differentiated 3T3-L1 adipocytes, also exhibited diminished adiponectin mRNA levels when exposed to low concentrations of H2O2. CONCLUSIONS/INTERPRETATION: Our results demonstrate that AngII-induced oxidative stress and endothelial dysfunction are accompanied by a decrease in adiponectin gene expression. Since antioxidants were observed to prevent the actions of AngII, and H2O2 on its own suppressed adiponectin expression, we conclude that adiponectin gene expression is negatively modulated by oxidative stress. Plasma adiponectin levels may provide a useful indicator of oxidative stress in vivo, and suppressed levels may contribute to the proinflammatory and metabolic derangements associated with type 2 diabetes, coronary artery disease and the metabolic syndrome.

Modulation of interleukin-8 and nitric oxide synthase mRNA levels by interferon-gamma in macrophages stimulated with lignin derivatives and lipopolysaccharides.

It has been shown that interferon-gamma (IFN-gamma) plays a role in the regulation of interleukin-8 (IL-8), nitric oxide (NO), and tumor necrosis factor-alpha (TNF-alpha) secretion by macrophages stimulated with lignin derivatives, such as EP3, and lipopolysaccharides (LPS) [Cytokine 11 (1999) 571]. To examine the mechanism by which IFN-gamma affects secretion of these factors, EP3- or LPS-stimulated macrophages were treated with different concentrations of IFN-gamma, and mRNA levels of IL-8, nitric oxide synthase (NOS) and TNF-alpha were determined by Northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). As reported previously, stimulation of macrophages by EP3 or LPS dramatically induced the expression of IL-8, NOS, and TNF-alpha mRNAs. IFN-gamma clearly decreased the level of IL-8 mRNA in stimulated macrophages, although it did not affect the IL-8 mRNA level in unstimulated macrophages. In contrast, IFN-gamma appeared to increase the level of NOS mRNA both in unstimulated and stimulated macrophages. IFN-gamma, which increased the amount of TNF-alpha mRNA in unstimulated macrophages, showed no significant effect on the high level of TNF-alpha mRNA in stimulated macrophages. These results suggest that IFN-gamma causes changes in IL-8 and NO secretion by stimulated macrophages through its effects on the level of IL-8 and NO mRNA, respectively. Effects of IFN-gamma on TNF-alpha secretion by stimulated macrophages may be mediated by a different mechanism.

Production of 5,8,11-eicosatrienoic acid by a delta5 and delta6 desaturation activity-enhanced mutant derived from a delta12 desaturation activity-defective mutant of Mortierella alpina 1S-4.

Enhanced production of 5,8,11-eicosatrienoic acid (Mead acid, 20:3omega9) was attained with a mutant fungus, Mortierella alpina JT-180, derived from delta12 desaturation activity-defective and delta6 desaturation activity-enhanced M. alpina M209-7. Production of 20:3omega9 by JT-180 was 1.4 times greater than that of the parent strain M209-7. This is thought to be due to its enhanced Delta5 desaturation activity, which was 3.3 times higher than that of M209-7. In both strains, 78.5-80.4% of the total lipids comprised triacylglycerol (TG), and 76.6-79.0% of 20:3omega9 was present in TG. Comparing the fatty acid compositions among various lipid species, the highest percentages (24.1-37.6%) of 20:3omega9 in total lipids were found in phosphatidylcholine. For optimization of 20:3omega9 production by JT-180, a glucose concentration of 4% in the culture medium and shifting of the growth temperature from 28 degrees C to 20 degrees C on the 2nd day were shown to be effective. Under optimal conditions, 20:3omega9 production by JT-180 reached 1.92 g/l culture medium in a 10-l jar fermentor (corresponding to 81.5 mg/g dry mycelia and 18.3% of total fatty acids), which is greater than that reported previously from M209-7 (1.65 g/l).

Expression of metastasis suppressor gene (KAI1/CD82) in oral squamous cell carcinoma and its clinico-pathological significance.

In this study, we investigated the expression of the KAI1/CD82 gene in oral squamous cell carcinoma (oral SCC). We studied 43 oral SCC patients. Reverse transcription-polymerase chain reaction (RT-PCR) analysis was performed to evaluate expression of this gene, and results were compared to the clinico-pathological findings. Twenty-five specimens (58.1%) were KAI1/CD82-positive, and 18 (41.9%) were negative. There were statistically significant relationships between gene expression and both histological malignancy (P=0.0205) and mode of invasion (P=0.0315). But there were no correlations of expression with tumor status, regional lymph node metastasis, pathological lymph node metastasis or histological differentiation. No significant relationship was observed between patient survival and expression of KAI1/CD82 by tumors. The results of this study suggest that the KAI1/CD82 gene may not be a useful predictor of prognosis, although decreased gene expression may be associated with increased invasive ability of oral SCC.

Dynamic changes in protein components of the tight junction during liver regeneration.

The construction of the hepatocyte tight junction is one of the most important events during liver regeneration leading to the reorganization of the bile canaliculi and the repolarization of hepatocytes after cell division. To understand this event at the molecular level, we examined the expression of tight junction proteins by Western blot analysis and their cellular localization by immunofluorescence microscopy in regenerating rat liver after two-thirds hepatectomy. The levels of tight junction components such as claudin-3, ZO-1 and atypical protein kinase C (PKC)-specific interacting protein (ASIP) increased two- to three-fold over control levels in coordination with a peak 2-3 days after partial hepatectomy, whereas occludin levels remained unchanged. The bile canaliculi outlined by tight junction components and actin filaments reveal significant morphological changes from 2-3 days after partial hepatectomy. During this period, claudin-3/ZO-1 and ASIP/ZO-1 were nearly co-localized, whereas occludin was locally reduced or almost absent on the bile canaliculi outlined by ZO-1 staining. The uncoupled localization of F-actin and tight junction components was often observed. The function of hepatocytes, as revealed by the serum bile acids level, was distorted temporally at an early stage of regeneration but mostly restored 3 days after partial hepatectomy. These observations suggest that the de novo construction of tight junctions proceeds mainly 2-3 days after partial hepatectomy in parallel with the cell polarization required for hepatocyte function. However, the complete normalization of the composition of the tight junction components, such as occludin and the association with F-actin, requires additional time, which may support the regeneration of fully polarized normal hepatocytes.

Suppression of platelet-activating factor generation and modulation of arachidonate metabolism by dietary enrichment with (n-9) eicosatrienoic acid or docosahexaenoic acid in mouse peritoneal cells.

Several studies have shown that dietary n-3 polyunsaturated fatty acids (PUFAs) suppress platelet-activating factor (PAF) generation in leukocytes of humans and rodents, which is associated with the antagonism of arachidonic acid metabolism. Dietary eicosatrienoic acid (20:3n-9, ETrA) is also suggested to antagonize arachidonic acid (AA) metabolism, but its effect on PAF generation in leukocytes has not been defined. In the present study, we investigated the effects of an ETrA-rich diet on PAF generation and AA metabolism in mouse peritoneal cells, which were compared with those of a docosahexaenoic acid (DHA)-rich diet. Mice were fed a diet supplemented with a lipid preparation rich in ETrA, a DHA-rich fish oil (FO) or palm oil (PO) for 3 weeks, and peritoneal cells containing more than 80% of monocytes/macrophages were obtained. The peritoneal cells in the DHA and ETrA diet groups generated upon zymosan stimulation a smaller amount of PAF than cells in the PO diet group. In the peritoneal cells of the DHA diet group, AA contents in phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were significantly lower than those in cells of the PO diet group, but those in phosphatidylinositol (PI) were not significantly different between the two dietary groups. A considerable amount of ETrA was incorporated into the peritoneal cells of the ETrA diet group, and AA was reduced as compared with the PO diet group. These changes occurred preferentially in PI but to a less extent in PC and PE. The amount of free AA released by the peritoneal cells upon zymosan stimulation was significantly reduced in the DHA diet group as compared with that in the PO diet group, whereas AA release was similar between the PO and ETrA diet groups. In conclusion, the effects of dietary ETrA on AA content in the phospholipid subclasses and AA release were quite different from those of dietary DHA, although both diets suppressed PAF generation in mouse peritoneal cells to a similar extent.

Biliary excretion of tauroursodeoxycholate-3-sulfate in the rat.

Biliary organic anion excretion is mediated by an ATP-dependent primary active transporter, multidrug resistance protein 2. On the other hand, a multiplicity of canalicular organic anion transport has been suggested. Ursodeoxycholic acid, the 7beta-epimer of chenodeoxycholic acid, is clinically used for various hepatobiliary diseases. In our previous study, the contribution of multidrug resistance protein 2 for biliary excretion of taurine-conjugated bile acid sulfates depended on the numbers of hydroxyl residue. Therefore, to further examine the effect of hydrophobicity on the substrate specificity of multidrug resistance protein 2, we examined the effect of bile acid conjugates and organic anions on biliary excretion of tauroursodeoxycholate-3-sulfate, taurine and sulfonate-conjugated ursodeoxycholic acid, in rats. Biliary tauroursodeoxycholate-3-sulfate excretions was markedly delayed in Eisai hyperbilirubinemic rats. Taurolithocholate-3-sulfate inhibited but ursodeoxycholate-3,7-disulfate did not affect biliary tauroursodeoxycholate-3-sulfate excretion. Biliary tauroursodeoxycholate-3-sulfate excretion was inhibited by sulfobromophthalein, but was not inhibited by dibromosulfophthalein and cefpiramide. These findings indicate that tauroursodeoxycholate-3-sulfate is very specific for multidrug resistance protein 2.