Different effect of testosterone and oestrogen on urinary excretion of metformin via regulating OCTs and MATEs expression in the kidney of mice.

The aim of this study was to investigate the effect of testosterone and oestrogen on regulating organic cation transporters (Octs) and multidrug and toxin extrusions (Mates) expression in the kidney of mice and urinary excretion of metformin. 8 week-old male db/db mice were treated with estradiol (5 mg/kg), testosterone (50 mg/kg) or olive oil with same volume. Metformin (150 mg/kg) was injected in daily for successive 7 days. Plasma, urine and tissue concentrations of metformin were determined by liquid chromatography-tandem mass spectrometry (LCMS) assay. Western blotting and Real-time PCR analysis were successively used to evaluate the renal protein and mRNA expression of Octs and MATEs. After treatment, the protein expression of Mate1 and Oct2 in testosterone group was significantly increased than those in control group (both P < 0.05). The protein expression of Mate1 and Oct2 in estradiol group was significantly reduced by 29.4% and 43.3%, respectively, compared to those in control group (all P < 0.05). These data showed a good agreement with the change in mRNA level (all P < 0.05). The plasma metformin concentration (ng/ml) in mice treated with estradiol was significantly higher than control and testosterone group (677.56 ± 72.49 versus 293.92 ± 83.27 and 261.46 ± 79.45; P < 0.01). Moreover, testosterone increased the metformin urine excretion of mice while estradiol decreasing (both P < 0.01). Spearman correlation analysis showed that gonadal hormone was closely associated with Mate1 and Oct2 expression and metformin urine excretion in db/db mice (all P < 0.05). Testosterone and oestrogen exerted reverse effect on metformin urinary excretion via regulating Octs and Mates expression in the kidney of mice.

The angiotensin-I converting enzyme gene I/D variation contributes to end-stage renal disease risk in Chinese patients with type 2 diabetes receiving hemodialysis.

Whether the DD genotype of the angiotensin-I converting enzyme (ACE) I/D variation contributes to end-stage renal disease (ESRD) risk in type 2 diabetes mellitus (T2DM) remains controversial. Differences in study design, case and control definition, sample size and ethnicity may contribute to the discrepancies reported in association studies. We performed a case-control study to evaluate the association of the ACE I/D variation with ESRD risk in Chinese patients with T2DM receiving hemodialysis and analyzed the genotype-phenotype interaction. Unrelated Chinese patients (n = 432) were classified into the non-diabetic nephropathy (DN) control group (n = 222, duration of diabetes >10 years, no signs of renal involvement) and the DN-ESRD group (n = 210; ESRD due to T2DM, receiving hemodialysis). Polymerase chain reaction was used to genotype ACE I/D for all 432 subjects. The frequencies of the ID + DD genotypes were higher in the DN-ESRD group than non-DN control group (65.2 vs. 50.9 %; adjusted OR 1.98 (95 % CI, 1.31-3.00; P = 0.001). In the DN-ESRD group, the DD genotypic subgroup had significantly elevated HbA1c and diastolic blood pressure (DBP) compared to the II subgroup (both P < 0.05). The DD genotype of the ACE I/D variation may be associated with more elevated blood pressure and HbA1c, and therefore may predict the development, progression and severity of DN-ESRD in Chinese patients with T2DM undergoing hemodialysis.

The E23K and A190A variations of the KCNJ11 gene are associated with early-onset type 2 diabetes and blood pressure in the Chinese population.

Conflicting associations between define (KCNJ11) variations and susceptibility to late-onset (>40 years old) type 2 diabetes mellitus (T2DM) have been reported in different ethnic groups. We investigated whether the E23K (G→A, rs5219) or A190A (C→T, rs5218) variations in KCNJ11 are associated with early-onset T2DM and blood pressure in the Chinese population. Case-control study of 175 unrelated Chinese patients with early-onset T2DM (age of onset <40 years old) who receive (ins+, n = 57) or do not receive insulin (ins-, n = 118), and 182 non-diabetic control subjects. PCR-direct sequencing was performed to genotype E23K and A190A; the genotypic frequencies and associations with clinical characteristics were analyzed. The genotypic frequencies of E23K-GA+AA were higher and A190A-TT was lower in the early-onset T2DM group, especially the T2D-ins+ group, compared to the non-diabetic control group (p < 0.01 or 0.05, respectively). In non-diabetic subjects, E23K-AA carriers had significantly higher 2 h plasma glucose and lower 2 h insulin than E23K-GG carriers (both p < 0.05). A190A-TT or E23K-GG carriers had higher systolic blood pressure (SBP) than CC or AA carriers in the non-diabetic control and T2DM groups (both p < 0.05). In the T2DM ins+ group, E23K-AA carriers had lower onset age and duration of diabetes and higher BMI than GG carriers, and A190A-TT carriers had higher SBP than CC carriers (all p < 0.05). The E23K-GA or AA genotypes may increase the susceptibility to early-onset T2DM, while A190A-TT may protect against early-onset T2DM. On the other hand the A190A-TT or E23K-GG genotypes may increase the risk of hypertension in the Chinese population.

The Leu72Met polymorphism of the GHRL gene prevents the development of diabetic nephropathy in Chinese patients with type 2 diabetes mellitus.

The preproghrelin (GHRL) Leu72Met polymorphism (rs 696217) is associated with obesity, reduced glucose-induced insulin secretion in healthy or diabetic subjects, and reduced serum creatinine (Scr) levels in type 2 diabetes. We evaluated the association of the Leu72Met polymorphism with measures of insulin sensitivity in non-diabetic control individuals and type 2 diabetics, and whether this variation contributes to the development of diabetic nephropathy (DN) in type 2 diabetes. A case-control study was performed of 291 non-diabetic control subjects and 466 patients with type 2 diabetes, of whom 238 had DN with overt albuminuria (DN group; albuminuric excretion rate [AER] ≥ 300 mg/24 h) and 228 did not have DN, but had diabetes for more than 10 years (non-DN group). Genotyping was performed using a TaqMan PCR assay. The Leu/Leu, Leu/Met, and Met/Met genotype frequencies were significantly different between the non-DN and DN groups (p = 0.011). The frequency of the variant genotypes (Leu/Met, Met/Met) was significantly lower in the DN group than the non-DN group (23.5 vs. 36.0 %, p = 0.003). Met/Met non-diabetic control subjects had lower BMI and Scr levels and higher eGFR level than Leu/Leu or Leu/Met individuals (p < 0.05). Leu/Met and Met/Met type 2 diabetics had significantly lower AER and Scr levels and higher eGFR level than Leu/Leu type 2 diabetics (all p < 0.001). The GHRL Leu72Met polymorphism may help to maintain normal renal function and may protect against the development of DN by reducing albuminuria and improving renal function in Chinese patients with type 2 diabetes.

Mutations in KCNJ11 are associated with the development of autosomal dominant, early-onset type 2 diabetes.

AIMS/HYPOTHESIS: More than 90% of Chinese familial early-onset type 2 diabetes mellitus is genetically unexplained. To investigate the molecular aetiology, we identified and characterised whether mutations in the KCNJ11 gene are responsible for these families. METHODS: KCNJ11 mutations were screened for 96 familial early-onset type 2 diabetic probands and their families. Functional significance of the identified mutations was confirmed by physiological analysis, molecular modelling and population survey. RESULTS: Three novel KCNJ11 mutations, R27H, R192H and S116F117del, were identified in three families with early-onset type 2 diabetes mellitus. Mutated KCNJ11 with R27H or R192H markedly reduced ATP sensitivity (E23K>R27H>C42R>R192H>R201H), but no ATP-sensitive potassium channel currents were detected in the loss-of-function S116F117del channel in vitro. Molecular modelling indicated that R192H had a larger effect on the channel ATP-binding pocket than R27H, which may qualitatively explain why the ATP sensitivity of the R192H mutation is seven times less than R27H. The shape of the S116F117del channel may be compressed, which may explain why the mutated channel had no currents. Discontinuation of insulin and implementation of sulfonylureas for R27H or R192H carriers and continuation/switch to insulin therapy for S116F117del carriers resulted in good glycaemic control. CONCLUSIONS/INTERPRETATION: Our results suggest that genetic diagnosis for the KCNJ11 mutations in familial early-onset type 2 diabetes mellitus may help in understanding the molecular aetiology and in providing more personalised treatment for these specific forms of diabetes in Chinese and other Asian patients.

Vibration perception threshold for sight-threatening retinopathy screening in type 2 diabetic outpatients.

OBJECTIVE: We investigated the relationship between vibration perception threshold and diabetic retinopathy and verified the screening value of vibration perception threshold for severe diabetic retinopathy. METHODS: A total of 955 patients with type 2 diabetes were recruited and divided into three groups according to their fundus oculi photography results: no diabetic retinopathy (n = 654, 68.48%), non-sight-threatening diabetic retinopathy (n = 189, 19.79%) and sight-threatening diabetic retinopathy (n = 112, 11.73%). Their clinical and biochemical characteristics, vibration perception threshold and the diabetic retinopathy grades were detected and compared. RESULTS: There were significant differences in diabetes duration and blood glucose levels among three groups (all p < 0.05). The values of vibration perception threshold increased with the rising severity of retinopathy, and the vibration perception threshold level of sight-threatening diabetic retinopathy group was significantly higher than both non-sight-threatening diabetic retinopathy and no diabetic retinopathy groups (both p < 0.01). The prevalence of sight-threatening diabetic retinopathy in vibration perception threshold >25 V group was significantly higher than those in 16-24 V group (p < 0.01). The severity of diabetic retinopathy was positively associated with diabetes duration, blood glucose indexes and vibration perception threshold (all p < 0.01). Multiple stepwise regression analysis proved that glycosylated haemoglobin (ß = 0.385, p = 0.000), diabetes duration (ß = 0.275, p = 0.000) and vibration perception threshold (ß = 0.180, p = 0.015) were independent risk factors for diabetic retinopathy. Receiver operating characteristic analysis further revealed that vibration perception threshold higher than 18 V was the optimal cut point for reflecting high risk of sight-threatening diabetic retinopathy (odds ratio = 4.20, 95% confidence interval = 2.67-6.59). CONCLUSION: There was a close association between vibration perception threshold and the severity of diabetic retinopathy. vibration perception threshold was a potential screening method for diabetic retinopathy, and its optimal cut-off for prompting high risk of sight-threatening retinopathy was 18 V.

Polymorphic variations in manganese superoxide dismutase (MnSOD), glutathione peroxidase-1 (GPX1), and catalase (CAT) contribute to elevated plasma triglyceride levels in Chinese patients with type 2 diabetes or diabetic cardiovascular disease.

Manganese superoxide dismutase (MnSOD), glutathione peroxidase-1 (GPX1), and catalase (CAT) provide the primary antioxidant defense system. Impaired antioxidant defense increases oxidative stress and contributes to the development of type 2 diabetes and diabetic cardiovascular disease (CVD). We preformed a case-control study in Chinese type 2 diabetes patients, to determine if the MnSOD Val16Ala (T→C), GPX1 Pro198Leu (C→T), and CAT -262C/T (C→T) functional polymorphisms contribute to the development of type 2 diabetes or diabetic CVD. Patients with type 2 diabetes (n = 168) were divided into the non-CVD group (n = 83, >10 year since diagnosis) and CVD group (n = 85, history of ischemic CVD). Genotyping was performed using PCR-restriction fragment length polymorphism (PCR-RFLP) or PCR-based direct sequencing. The genotypic distribution in the non-CVD- and CVD-group and the clinical parameters in genotypic groups were not significantly different in the three polymorphic sites, respectively. Among eight genotypic combinations, the most common TT+CC+CC genotype (59.5%) was associated with higher triglyceride levels than the TT+CT+CC genotype, the second frequent one (14.9%; 1.77 ± 0.12 vs. 1.21 ± 0.11 mmol/l, P = 0.001), and all non-TT+CC+CC genotypes (40.5%; 1.77 ± 0.12 vs. 1.43 ± 0.12 mmol/l, P = 0.048). In the CVD group, significantly elevated triglyceride levels were also observed in patients with TT+CC+CC compared to patients with TT+CT+CC (2.00 ± 0.18 vs. 1.37 ± 0.16 mmol/l, P = 0.018) or non-TT+CC+CC genotypes (2.00 ± 0.18 vs. 1.65 ± 0.19 mmol/l, P = 0.070). The common MnSOD, GPX1, and CAT TT+CC+CC genotype may contribute to hypertriglyceridemia in Chinese patients with type 2 diabetes or diabetic CVD.

SLC22A2 gene 808 G/T variant is related to plasma lactate concentration in Chinese type 2 diabetics treated with metformin.

AIM: To investigate the potential relationship between the SLC22A2 gene polymorphism and blood lactate concentration in Shanghai Hans suffering from type 2 diabetes mellitus (T2DM). METHODS: The SLC22A2 single nucleotide polymorphism (SNP) 808G/T was genotyped in 400 T2DM patients, including a metformin-treated group (n=200) and a non-metformin-treated group (n=200). Fasting plasma lactic acid levels were measured with an enzyme-electrode assay. Biochemical indexes, including plasma alanine aminotransferase (ALT), creatinine (Cr), and glycolated hemoglobin (HbA1c), were also measured. RESULTS: The fasting plasma lactate concentration in the metformin-treated group was significantly higher than that in the non-metformin-treated group (1.29+/-0.45 mmol/L vs 1.18+/-0.44 mmol/L, P=0.015). Additionally, the ratio of patients with hyperlactacidemia was 8% (16/200) for the metformin-treated group and 5.5% (11/200) for the non-metformin-treated group, with no lactic acidosis found in either group. The frequency of the SLC22A2 808G/T T allele was 12.9%. Patients with the mutant genotype (TT) had a higher blood lactate concentration in the metformin-treated group than those in the non-metformin-treated group (t=2.492, P=0.013). This trend was not observed in the GG and GT genotypes when compared with metformin-treated and non-metformin-treated groups. Patients with the mutant genotype (TT) in the metformin-treated group also had a higher incidence of hyperlactacidemia compared with the GG genotype (40.0% vs 6.9%, P=0.050) in the metformin-treated group and the GG (6.0%, P=0.042) or GT (4.3%, P=0.043) genotypes in the non-metformin-treated group. In the metformin-treated group, there were significant gender differences in lactate concentrations in the TT (2.18+/-0.15 vs 1.04+/-0.27 mmol/L, P=0.008) and GG genotypes (1.40+/-0.51 vs 1.19+/-0.35 mmol/L, P=0.004). The lactate levels of women with the TT genotype were the highest in the metformin-treated group, but differences in lactate levels among the genotypes were not observed in the non-metformin-treated group. CONCLUSION: There is an 808G/T polymorphism in the SLC22A2 gene in Chinese Hans with T2DM. The 808G>T variance in the SLC22A2 gene can affect the plasma lactate level and the incidence of hyperlactacidemia in T2DM patients undergoing metformin therapy. Additionally, the female patients carrying the TT genotype are prone to lactatemia.

The manganese superoxide dismutase Val16Ala polymorphism is associated with decreased risk of diabetic nephropathy in Chinese patients with type 2 diabetes.

The aim of the present study was to evaluate the relationship of the manganese superoxide dismutase (MnSOD) Val16Ala (V16A) polymorphism with type 2 diabetes mellitus (T2DM) and diabetic nephropathy (DN) in Chinese patients, a case-control study was performed. This case-control study included 172 non-diabetic (non-DM) subjects and 257 T2DM patients with or without DN. Among T2DM patients, 154 had DN [albumin excretion rate (AER) >or= 30 mg/24 h] and 103 did not (AER < 30 mg/24 h), but the latter with known diabetes duration >or=10 years. The DN patients were further divided into groups with microalbuminuria (DN-1; n = 92; 300 > AER >or= 30 mg/24 h) and overt albuminuria nephropathy (DN-2; n = 62; AER >or= 300 mg/24 h). PCR-restriction fragment length polymorphism (RFLP) was used to detect genotypes of the V16A polymorphism for all subjects. The genotypic distributions of the V16A polymorphism in non-DM and T2DM subjects were in Hardy-Weinberg equilibrium and Ala allelic frequencies did not differ (11.9% vs. 9.1%; P > 0.05). The AA+VA genotypic frequencies of DN patients were significantly lower than those of non-DN patients (11.6% vs. 24.3%; P = 0.008). Multiple logistic regression analysis revealed that except for HbA1C, triglyceride, and BMI, which were high risk factors for the development of DN, the AA+VA genotype of the MnSOD-V16A polymorphism was an independent protective factor from the development of DN (odds ratio = 0.42; 95% CI = 0.18-0.95; P = 0.037) in T2DM patients. Our results suggested that the MnSOD-V16A polymorphism is associated with decreased risk of diabetic nephropathy in Chinese patients with type 2 diabetes.

[Study on the mitochondrial DNA mutations in familial diabetes mellitus in Chinese population].

OBJECTIVE: To assess the prevalence of mutations or variants of the mitochondrial DNA (mtDNA) in familial diabetes mellitus in Chinese population, and to explore the relationship between mtDNA mutations or variants and diabetes. METHODS: Seven hundred and seventy randomly selected, unrelated probands of diabetes pedigrees and 309 controls over 60 years of age with normal glucose tolerance were recruited. PCR-RFLP and PCR-direct sequencing were applied to the screening of mtDNA mutations or variants, including the mutations at nucleotides 3243, 3256 in tRNALeu region, 12258 in tRNASer region, 14709 in tRNAGlu region, 8296, 8344, 8363 in tRNALys region, 3316, 3394, 3426 in ND1 region and 12026 in ND4 region. RESULTS: In the diabetic group, 13 (1.69%) had mt3243 A>G mutation, 9(1.17%) had tRNAGlu 14709 T>C variant, 17 (2.21%) carried mt3316 G>A variant, 18 (2.34%) had mt3394 T>C variant, and 28 (3.63%) harbored the 12026 A>G variant. In the control group, the 14709, 3316, 3394, 12026 variants were detected in 5(1.62%), 5(1.62%), 6(1.94%), and 9(2.91%) subjects respectively. The 3256, 8296, 8344, 8363, 3426 and 12258 point mutations were not detected both in the diabetic patients and the controls. In the diabetic group, we found two double mutations, one was A3243G and T3394C, the other was A3243G and A12026G. Except that the A3243G mutation was only observed in the diabetic group, the frequencies of the other variants mentioned above were not statistically different between the diabetic and control groups. Moreover, clinical characteristics such as age of onset, BMI, and insulin resistance index were not different between diabetic patients with and without the variants. CONCLUSION: The tRNA (LeuUUR) 3243 A>G mutation may be the major cause of diabetes, representing 1.69% of the familial diabetes mellitus in Chinese. The other variants may be polymorphisms in this population, and the mutations not detected in our studied population may not be common contributors to diabetes mellitus in Chinese.

[Prevalence and clinical characteristics of the mitochondrial tRNA(Leu(UUR)) gene 3243 A to G mutation in familial diabetes mellitus in Chinese population].

OBJECTIVE: To study the prevalence and clinical characteristics of the A to G mutation at nucleotide 3243 of the mitochondrial tRNA(Leu(UUR)) gene in familial diabetes in Shanghai, Jiangsu and Zhejiang Province of China. METHODS: The mt3243 A to G mutation in 770 randomly selected, unrelated probands of diabetic pedigrees were screened by PCR-RFLP technique and PCR-direct sequencing. Genetic and clinical analyses were further performed in the probands and their family members. RESULTS: Thirteen diabetic patients (13/770, 1.69%) with mt3243 A to G mutation were detected. Eleven diabetic patients and 8 normal glucose tolerance (NGT) first-degree relatives of these 13 probands were also found bearing the mutation. Seventeen patients were associated with sensory hearing loss. In the 24 patients harboring the mutation, the majority had lower body mass index (BMI), 18 showed typical maternal inheritance, 15 had sensory hearing loss, 13 had insulin resistance and 14 required insulin therapy due to secondary failure to oral hypoglycemic agents. CONCLUSION: The mutation of mt3243 A to G in the mitochondrial tRNA(Leu(UUR)) gene is an important cause of diabetes in Shanghai, Jiangsu and Zhejiang Province of China. Mitochondrial gene mutation diabetes (MDM) is clinically characterized by early onset, emaciation, maternal inheritance, sensorineural hearing loss, and lower islet beta cell function, and some have insulin resistance.

Insights into pathogenesis of five novel GCK mutations identified in Chinese MODY patients.

OBJECTIVE: Heterozygous inactivating mutations in GCK are associated with defects in pancreatic insulin secretion and/or hepatic glycogen synthesis leading to mild chronic hyperglycaemia of maturity onset diabetes of young type 2 (MODY2). However, the effect of naturally occurring GCK mutations on the pathogenesis for MODY2 hyperglycaemia remains largely unclear, especially in the Asian population. The aim of this study is to explore the potential pathogenicity of novel GCK mutations related to MODY2. METHODS: Genetic screening for GCK mutations from 96 classical MODY families was performed, and structure-function characterization and clinical profile of identified GCK mutations were conducted. RESULTS: Five novel (F195S, I211T, V222D, E236G and K458R) and five known (T49N, I159V, R186X, A188T and M381T) mutations were identified and co-segregated with hyperglycaemia in their pedigrees. R186X generates non-functional truncated form and V222D and E236G fully inactivate glucokinase due to severe structure disruptions. The other seven GCK mutations exhibited marked reductions in catalytic efficiency and thermo-stability; notably, the interaction with GKRP was significantly enhanced in I211T, I159V, T49N and K458R, reduced in F195S and M381T, and completely lost with A188T. 31% (17/55) of MODY2 patients showed signs of insulin resistance. Conventional hypoglycaemia treatment did not improve the HbA1C in MODY2 patients when insulin resistance is not present. CONCLUSIONS: Five novel GCK mutations have been identified in Chinese MODY. The defects in enzymatic activity and protein stability, together with alteration of GKRP binding on GCK mutants may synergistically contribute to the development of MODY2 hyperglycaemia. No treatment should be prescribed to MODY2 patients when insulin resistance is not present.

[The genetic and clinical characteristics of transcription factor 1 gene mutations in Chinese diabetes].

OBJECTIVE: To investigate the genetic and clinical features of mutations and sequence variations of the transcription factor 1 gene (TCF1, HNF-1A) in Chinese with familial early-onset and/or multiplex diabetes mellitus. METHODS: All ten exons of the TCF1 gene were screened, including exon and intron junctions, by direct sequencing method in 341 unrelated Chinese subjects, including 80 healthy controls and 261 probands of early-onset and/or multiplex diabetes pedigrees. RESULTS: Five mutations were found in all. Four of the 5 different TCF1 mutations were newly identified novel mutations(T82M, Q130H, G253G, P353fsdelACGGGCCTGGAGC), mean body mass index of mutation carriers was 21.9 kg/m (2), and insulin secretion was impaired in the mutation carriers. In this study, the maturity-onset diabetes of the young type III (MODY3) only accounted for 3% of Chinese early-onset diabetes. Moreover, eleven substitutions were identified in 261 probands. Of them, three variants IVS1-8 (G-->A), IVS1 -128 (T-->G ) and IVS2+21 (G-->A) were not observed in 80 healthy controls and one of them IVS1-8 (G-->A) was not reported previously and the two promoter variants co-segregated with diabetes. CONCLUSION: TCF1 gene is not a common cause of early-onset and/or multiplex diabetes among Chinese patients.

Identification of four novel mutations in the HNF-1A gene in Chinese early-onset and/or multiplex diabetes pedigrees.

BACKGROUND: Mutations in the hepatocyte nuclear factor-1A gene cause the type 3 form of maturity-onset diabetes of the young (MODY3). This study was undertaken to determine mutations and sequence variations of the HNF-1A gene in Chinese with familial early-onset and/or multiplex diabetes mellitus. METHODS: We screened all ten exons of the HNF-1A gene, including exon/intron junctions, by direct sequencing in 272 unrelated Chinese, including 80 healthy controls and 192 probands of early-onset and/or multiplex diabetes pedigrees. RESULTS: In addition to one silent mutation of c.864 G > C [p.G288G] in exon4 at codon 288, which had been reported previously, a total of four novel mutations including two missense mutations (c.245C > T [p.T82M] and c. 390 G > T [p.Q130H]) and one frameshift mutation P353fsdelACGGGCCTGGAGC and one silent mutation c.759 G > T [p.G253G] were identified. Moreover, eleven substitutions were identified in 192 probands. Of these, three variants (-8 G > A, -128 T > G and IVS2 + 21 G > A) were not observed in 80 healthy controls and one of them (-8 G > A) was not reported previously and the two promoter variants co-segregated with diabetes. The genotype and allele frequencies of the other eight variants in the diabetic patients were not significantly different from those in the healthy controls. No significant relationships were observed between the eight variants of the HNF-1A gene and clinical variables (plasma glucose, insulin, C-peptide and fasting lipid profile). CONCLUSION: The prevalence of structural mutations in the HNF-1A gene responsible for familial early-onset and/or multiplex diabetes appears to be rare among Chinese patients.

[Prevalence and clinical characteristics of the A to G variant at position 12026 of the mitochondrial ND4 gene in familial diabetes mellitus in Chinese population].

OBJECTIVE: To assess the prevalence of the A to G variant at nucleotide 12026 (mt12026) of the mitochondrial NADH-dehydrogenase subunit 4 (ND4) gene in familial diabetes mellitus in Chinese population. METHODS: The authors screened 770 randomly selected, unrelated probands of diabetic pedigrees, and 309 controls with normal glucose tolerance for the variant by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique and PCR-direct-sequencing. RESULTS: The mt12026 A --> G variant was detected in 28 diabetic patients (3.63%) and 9 controls (2.91%). The frequency of the variant mt12026 A --> G was not statistically different between diabetic patients and controls. Moreover, clinical characteristics such as age, body mass index (BMI), and insulin resistant index were not different between diabetic patients with and without the mt12026 mutation. CONCLUSION: The mt12026 A --> G variant is a mitochondrial gene polymorphism in Chinese population, and it is unlikely that the mutation is in itself the cause of diabetes.

Genome-wide search for type 2 diabetes/impaired glucose homeostasis susceptibility genes in the Chinese: significant linkage to chromosome 6q21-q23 and chromosome 1q21-q24.

This genome-wide search for susceptibility genes to type 2 diabetes/impaired glucose homeostasis (IGH) was performed on a relatively homogeneous Chinese sample with a total number of 257 pedigrees and 385 affected sibpairs. Two regions showed significant linkage to type 2 diabetes/IGH in the Chinese. The region showing linkage to type 2 diabetes/IGH from the entire sample group analysis was located on chromosome 6q21-q23 (128.93 cM, 1-LOD [logarithm of odds] support interval between 124 and 142 cM, according to the Marshfield genetic map), with a maximum likelihood score of 6.23, a nonparametric linkage (all) score of 4.48, and empirical P value <0.001. With a subanalysis based on 101 affected sibpairs with age at diagnosis of type 2 diabetes/IGH <40 years, we detected significant evidence for linkage to chromosome 1q21-q24 (192.1 cM, 1-LOD support interval between 182 and 197 cM), with a maximum likelihood score of 8.91, a nonparametric linkage (all) score of 5.70, and empirical P value <0.001. No interaction was observed between these two regions. Our independent replication of the region on chromosome 1q that has been shown to be linked significantly to type 2 diabetes/IGH in Chinese supports the notion that gene(s) in this region may be universally important in the development of human type 2 diabetes.

[Mutation screening of GCK gene in Chinese early-onset diabetes population].

OBJECTIVE: To investigate the prevalence of mutations and sequence variations of glucokinase gene GCK in Chinese early-onset diabetes population. METHODS: The study was conducted in 174 unrelated Chinese residents, including 80 nondiabetic controls, 94 probands of early-onset diabetes pedigree. Direct sequencing was performed to screen all 10 exons of glucokinase gene, including promoter and exon/intron junctions. RESULTS: No mutations were identified in coding region, but several previously reported sequence variants were identified. 5'-untranslated region of exon 1a, 84 bp upstream of the translation initiation site GGCGG to GGGGG(early-onset diabetes group G allele frequency 0.106 vs control group 0.075, P=0.355); IVS1b+12 (A-->T) (early-onset diabetes group T allele frequency 0.005 vs non-identity of this variation in control group); IVS 5+29 (G-->T) (early-onset diabetes group T allele frequency 0.027 vs control group 0.019, P=0.731); IVS 9+8 (T-->C) (early-onset diabetes group C allele frequency 0.585 vs 0.694, P=0.044). A novel variation IVS 9+49 (G-->A) (early-onset diabetes group A allele frequency 0.011 vs control 0.006, P=1.000) was identified. There were no significant relationships of the exon 1a 5'-untransted region -84 bp(C-->G), IVS 5+29 (G-->T), IVS 9+8 (T-->C) and IVS 9+49 (G-->A) variants of GCK gene to the clinical variables such as plasma glucose, insulin, C-peptide and fasting lipid profile. CONCLUSION: The prevalence of structural mutations in glucokinase gene responsible for early-onset diabetes appears to be rare among Chinese patients.

SLC47A1 gene rs2289669 G>A variants enhance the glucose-lowering effect of metformin via delaying its excretion in Chinese type 2 diabetes patients.

AIMS: The SLC47A1 gene encodes the multi-drug and toxic excretion-1(MATE1) protein, which plays a key role in the transport and excretion of metformin. This study is to clarify the influence of variants in SLC47A1 (rs2289669 G→A) on metformin pharmacokinetics and the long-term glucose-lowering effect of metformin. METHODS: A total of 220 newly diagnosed type 2 diabetes patients were recruited, genotyped and divided into three groups by SLC47A1 genotypes (G/G, G/A, A/A). Ten patients in each group were randomly selected for metformin pharmacokinetics. All the participants received metformin oral treatment and were followed for one year. RESULTS: After one-year follow-up, the decline of HbA1c level was significantly greater in subjects with variant genotype (AA) than other two groups (-2.32% [-25.4 mmol/mol] in AA vs. -1.16% [-12.7 mmol/mol] in GA, -1.07% [-11.7 mmol/mol] in GG, P<0.05). Then taking GG genotype as the referent, the association between AA genotype and change of HbA1c still existed after adjusted for age, sex, BMI, baseline HbA1c and diabetes duration (P<0.05). Pharmacokinetic parameters of metformin indicated that patients carrying MATE1 homozygous A had higher area under the plasma concentration versus time curve (AUC12h), but lower renal clearance (CLR) and renal clearance by secretion (CLSR) than other patients (all P<0.01). Multivariate lineal stepwise analysis further revealed that SLC47A1 genotype was an independent impact factor for urine excretion of metformin (P<0.01). CONCLUSIONS: SLC47A1 rs2289669 G>A variants improve the glucose-lowering effect of metformin through slowing its excretion in type 2 diabetes populations.

Metformin reduces serum CA199 levels in type 2 diabetes Chinese patients with time-effect and gender difference.

BACKGROUND: This study was designed to clarify the influence of metformin on serum carbohydrate antigen 199 (CA199) levels and its associated factors in Chinese type 2 diabetes mellitus (T2DM) patients. SUBJECTS AND METHODS: In total, 1,253 T2DM patients were enrolled, including a non-metformin group (n = 616), a short-term metformin group (at least 1 week to 2 years; n=325), and a long-term metformin group (≥ 2 years; n = 312). Their clinical and biochemical characteristics were collected and compared. After 1 year, the biochemical parameters were re-examined in 296 patients. Sex hormones were determined, and associations between CA199 and other variables were assessed. RESULTS: At baseline, the incidence of abnormal CA199 levels was 14.7%, 8.9%, and 4.7% in the non-metformin, short-term metformin, and long-term metformin groups, respectively. CA199 levels in females were significantly higher than in males (P < 0.01) and decreased significantly with the time of taking metformin (25.60 ± 13.68 U/mL in non-metformin controls vs. 17.62 ± 10.87 U/mL in the short-term group vs. 10.54 ± 8.14 U/mL in the long-term group; P = 0.000). The correlation and multiple stepwise regression analysis revealed that glycosylated hemoglobin, metformin, gender, total cholesterol, and follicle-stimulating hormone were independent impact factors on CA199 concentrations (all P < 0.05). Binary logistic regression revealed that the risk of abnormal CA199 concentrations of the total population with short-term metformin or long-term metformin treatment decreased 11% (odds ratio = 0.89; P = 0.001) and 30% (odds ratio = 0.70; P = 0.000), respectively, at baseline. After a 1-year follow-up, the incidence of high CA199 level decreased in both the short-term and the long-term metformin group compared with that of controls (P < 0.05). The extent of CA199 decrease in the long-term metformin group was the greatest (-17% vs. -4.9% in the short-term group vs. 3% in controls, P = 0.000), and the group's risk of high blood CA199 level was reduced 67% (odds ratio = 0.33; P = 0.023). The reduction in women was more apparent than that in men (-18% vs. -5%, P = 0.000). CONCLUSIONS: Metformin therapy reduced the CA199 level in Chinese T2DM patients, and its greatest decrease occurred in women with longer therapeutic time.

Polymorphism of organic cation transporter 2 improves glucose-lowering effect of metformin via influencing its pharmacokinetics in Chinese type 2 diabetic patients.

BACKGROUND AND OBJECTIVES: This study aimed to investigate how the organic cation transporter 2 nucleotide polymorphism at site 808 (G → T) affects metformin pharmacokinetics and its long-term anti-diabetic effect. METHODS: A total of 220 newly diagnosed type 2 diabetes patients taking oral metformin were recruited, genotyped and then divided into three groups by SLC22A2 genotypes (G/G, G/T, T/T). Nine patients in the GG genotype group, five patients in the GT genotype group and four patients in the TT genotype group were randomly selected for the metformin pharmacokinetic study. A randomized cohort study with 1-year follow-up was performed to clarify the metformin pharmacodynamics. RESULTS: After 1 year, the decrease in glycosylated hemoglobin (HbA1c) levels in subjects with the heterozygous variant genotype (GT) was significantly greater than in those with the wild-type homozygote (-2.2 % in GT vs. -1.1 % in GG, P < 0.05) after adjustment for baseline HbA1c levels, exercise and diet in each group. There were also differences in the pharmacokinetic parameters (95 % confidence interval) of metformin between these two groups [area under the concentration-time curve (AUC)0-∞ 19.7 (15.7-23.8) vs. 14.3 (11.7-16.9) µg h/L; renal clearance (CLr) 16.8 (8.5-25.0) vs. 34.1 (24.9-43.2) L/h; tubular secretion clearance (CLt) 8.1 (2.2-18.1) vs. 22.7 (15.5-29.8) L/h; all P < 0.05]. Multivariate analysis further revealed that the presence of T alleles and gender were independent influencing factors of urine excretion of metformin (P < 0.05). CONCLUSION: As well as gender, the glucose-lowering efficiency of metformin can be enhanced by SLC22A2 808G > T variants through the delay of its transportation and CLr in Chinese type 2 diabetes populations.