Metabolic and endocrine studies in a case of lipoatrophic diabetes

A 20-yr-old female with congenital lipoatrophic diabetes was studied, with the following findings: (1) Serum insulin levels increased after both oral glucose and intravenous arginine administration; there was no growth hormone response to the latter. (2) The infusion of insulin (0.1 units and 0.5 units/kg) during the fed state and following a 110-hr fast produced only minimal changes of various fuels measured, with the exception of a decrease in the branched-chain amino acids. (3) There was a minimal production of ketones during the 110-hr fast. (4) Metabolic expenditure was markedly increased during the postabsorptive state (65–75 kcal/hr/sq m); it fell into the normal range during the 110-hr fast (31–35 kcal/hr/sq m). (5) Following meals, the patient experienced complaints ranging from cold and shivering to feeling hot with gross diaphoresis. These findings were associated with intermittent lability of her skin temperature, which varied 1°–2°F during a 3-hr period. (6) Progressive increases in doses of regular insulin before each meal resulted in up to a total of 9000 units/day being required before normal blood glucose levels were achieved. (7) A 2-wk therapeutic trial of pimozide provided no significant changes in a variety of hormones and fuels in the basal state or following insulin perturbations. (8) A variety of pituitary hormones and pituitary target organ hormones were studied in both the hypothyroid (Hashimoto's thyroiditis) and euthyroid state (following thyroid replacement). All the hormone responses were normal except that growth hormone did not rise during the slow wave sleep in either thyroid state.     

The effect of diet upon carbohydrate metabolism, insulin resistance, and blood pressure in congenital total lipoatrophic diabetes

An 11-yr-old female with congenital total lipodystrophy had nonketotic hyperglycemia with resistance to both endogenous and exogenous insulin and systemic hypertension. Twenty-four hour patterns of secretion and mean concentrations of growth hormone, cortisol, Luteinizing Hormone (LH), and Follicle-Stimulating Hormone (FSH) were normal. Plasma glucagon was elevated during periods of hyperglycemia, but was normal during normoglycemia, even though insulin resistance was still evident. Insulin receptor density and affinity for insulin as determined in monocytes and erythrocytes were normal during hyperglycemia. Therapy with insulin and pimozide were not effective in controlling hyperglycemia. However, a diet restricted to 1800–2000 cal per day of average sodium content resulted in euglycemia and normal blood pressure without insulin therapy. Fasting serum glucose decreased from 393 to 65 mg/dl. In addition, triglycerides decreased from 304 to 115 mg/dl, glucagon from 421 to 126 pg/ml, and liver size returned to normal. There was a correlation between blood pressure and fasting glucose: systolic, r = 0.725, n = 54, p < 0.001; diastolic, r = 0.424, n = 54, p < 0.001. Plasma renin activity (PRA) and plasma aldosterone (PA) levels were mildly elevated in both the hypertensive and normotensive states. Plasma renin activity was 2.15 ± 0.73, (SD) ng/ml/hr supine and 5.32 ± 1.81 upright over an 11-day period when urinary sodium excretion was 96.0 ± 25.5 meq/day. When fasting glucose levels were 332–393 mg/dl, glucose turnover was 1967 μmole/min (normal, 696 ± 120, SD), net glucose decay during i.v. glucose tolerance (IVGTT) 15.6 g/50 min/1.73m² (normal, 16.7 ± 3.7), and Kg was 0.52%/min (normal, 1.86 ± 0.51, SD). After intensive diet therapy, fasting glucose was 97 and glucose turnover was 810 μmole/min, net glucose decay was 15.18 and Kg was 0.92. When the subject was hyperglycemic, plasma alanine concentration was normal, as was alanine conversion to glucose. Basal unbound insulin levels were elevated during hyperglycemia and normal during euglycemia. Insulin release, which was negligible during the first IVGTT, had a more normal pattern during the second test. In this patient with lipoatrophy, insulin resistance did not appear to derive from known insulin antagonists. The data suggested that insulin resistance may derive from a reversible loss of coupling of a normal insulin receptor to metabolic pathways. This loss may be tissue specific, involving adipose tissue and liver but not muscle, and appears to occur at insulin levels that are increased but lower than would otherwise cause a loss of hormone responsiveness in normal and obese individuals. An unknown antagonist, if present, must be diet-dependent.     

Cell culture studies of a patient with congenital lipoatrophic diabetes—Normal insulin binding with alterations in intracellular glucose metabolism and insulin action

Insulin binding and the action of insulin on several aspects of glucose metabolism have been investigated in cultured fibroblasts derived from a patient with congenital lipoatrophic diabetes and compared to cultures from 9 nondiabetic controls. Incorporation of glucose was elevated in the patient's cells at glucose levels above 0.1 mM. When distribution of labelled glucose was examined, cell associated glycogen and acid soluble material were increased, but the greatest increment was in lactate production. Insulin binding, as indicated by maximum specific ¹²⁵I-insulin binding and concentration of unlabelled insulin for 50% displacement, was normal, although insulin regulation of the insulin receptor was diminished. Insulin stimulation of total glucose incorporation was reduced in cells from the patient. When insulin stimulation of glycogen synthase was measured directly, the response to insulin was also attenuated. On the other hand, insulin stimulation of hexose transport appeared to be unimpaired. The data indicate alterations in both cell glucose metabolism and insulin response which may be related to the observed insulin resistance of this disorder.     

Anomalous leucine metabolism in total lipoatrophic diabetes: a possible mechanism of muscle mass hypertrophy

Total acquired lipoatrophic diabetes (LD) is characterized by muscle mass hypertrophy, non-ketotic hyperglycaemia and insulin resistance with respect to glucose and lipid metabolism. To assess whether the defect in insulin action extends to leucine/protein metabolism, a female subject (age=33 years; body weight=44 kg; HbA_lc=9.5%) with LD was studied twice: in study I we used a three-step euglycaemic hyperinsulinaemic clamp (40, 80 and 200 mU · m^–2 · min^–1) combined with [3-³H]glucose and [1-¹⁴C]leucine infusions along with indirect calorimetry. In study II we used a 40 mU · m^–2 · min^–1 euglycaemic hyperaminoacidaemic (plasma leucine 160 mol/l) hyperinsulinaemic clamp. Five controls were also studieD. In the basal state the patient with LD had plasma leucine (130 mol/l), isoleucine (63), valine (169) and phenylalanine levels (48) comparable to those of the controls. Basal hepatic glucose production (3.2 vs 2.0±0.2 mg · kg^–1 · min^–1), endogenous leucine flux (ELF=45.4 vs 40±1 mol · m^–2 · min^–1) and non-oxidative leucine disposal (NOLD=37.2 vs 34±1 mol · m^–2 · min^–1) were increased in the patient with LD, while basal leucine oxidation (LO=8.2 vs 6.0±2 mol · m^–2 · min^–1) was similar in LD and controls. Following the three-step insulin infusion, insulin-stimulated glucose metabolism was defective in the subject with LD (glucose oxidation=60%, 50%, and 52% of controls; non-oxidative glucose disposal =39%, 34% and 30% of controls at 40, 80 and 200 mU · m^–2 · min^–1 respectively). The decrease of leucine, isoleucine, valine and phenylalanine, as well as the suppression of ELF, LO and NOLD was defective in the subject with LD at each insulin step. In vitro studies demonstrated a defect in receptor insulin binding on erythrocytes, the absence of anti-insulin receptor antibodies and the presence of insulin antibodies in the serum of the patient with LD. Following combined hyperaminoacidaemia/hyperinsulinaemia a similar stimulation of protein synthetic rate (20 vs 30%) was demonstrated in the patient with LD and controls respectively. In conclusion the patient with LD shows a reduced insulin sensitivity and a reduced maximal response to insulin in both glucose and protein metabolism. The present data support the hypothesis that in LD the defect in insulin action is both at the receptor and post-receptorial sites. The patient with LD showed a normal stimulation of protein synthesis under combined hyperinsulinaemic/hyperaminoacidaemic conditions. Our results may explain the muscle mass hypertrophy in LD.     

高脂饲养大鼠脂代谢调控基因的表达与胰岛素抵抗的关系及机制

目的探讨高脂饲养SD大鼠脂代谢基因表达的改变与胰岛素抵抗（IR）的关系。方法8周龄雄性SD大鼠随机分为3组：正常饲养组（NC,10只）、高脂饲养组（HF,10只）、高脂饲养＋吡格列酮15mg·kg^-1·d^-1进行灌胃组（HP,12只）。饲养20周时测定血清、肝脏及肌肉组织中TG含量,3组均行正常血糖高胰岛素钳夹试验,并用实时定量PCR方法分析脂肪、肝脏和肌肉中脂代谢调控基因mRNA表达的变化。结果饲养20周时,与NC组比较,HF组血清TG增加45．0％（P〈0．01）,肝脏和肌肉TG含量增加2．28倍和9．31倍（P〈0．01）;HF组葡萄糖的输注率（GIR）下降61％（P〈0．01）,存在明显的IR;脂肪组织脂肪酸合成酶、激素敏感酯酶表达分别增高21．3％、28．2％（P〈0．05）;肝脏乙酰辅酶A羧化酶表达增高48．3％（P〈0．05）、肉毒碱脂酰转移酶1（CPT-1）表达呈增高趋势（P〉0．05）;肌肉乙酰辅酶A羧化酶表达增加101．1％、CPT-1表达减少71．0％（P〈0．01）。HP组与HF组比较,血TG、肝脏TG、肌肉TG分别下降66．0％、64．5％及59．6％,GIR增加1．54倍,脂代谢基因的表达也发生了明显的改变。结论高脂饲养可引起sD大鼠肝脏和肌肉组织脂肪异位沉积及IR,吡格列酮干预可以改善,可能与脂代谢调控基因的改变有关。     

PPARδ与脂代谢及胰岛素抵抗

过氧化物酶体增殖物活化受体(PPAR)δ是新近发现与脂代谢及胰岛素抵抗相关的转录因子,属PPAR家族。PPARδ存在多种配体。动物试验表明,激活PPARδ可以改善血脂谱及胰岛素敏感性。PPARδ通过调节脂代谢所需酶的表达来调控机体的脂代谢,并调节胰岛素的敏感性。PPARδ的基因多态性研究也提示其与血脂、血糖、体重指数相关。PPARδ可能是调控脂代谢及胰岛素敏感性的关键因子。     

Leptin improves insulin resistance and hyperglycemia in a mouse model of type 2 diabetes

Leptin has metabolic effects on peripheral tissues including muscle, liver, and pancreas, and it has been successfully used to treat lipodystrophic diabetes, a leptin-deficient state. To study whether leptin therapy can be used for treatment of more common cases of type 2 diabetes, we used a mouse model of type 2 diabetes (MKR mice) that show normal leptin levels and are diabetic due to a primary defect in both IGF-I and insulin receptors signaling in skeletal muscle. Here we show that leptin administration to the MKR mice resulted in improvement of diabetes, an effect that was independent of the reduced food intake. The main effect of leptin therapy was enhanced hepatic insulin responsiveness possibly through decreasing gluconeogenesis. In addition, the reduction of lipid stores in liver and muscle induced by enhancing fatty acid oxidation and inhibiting lipogenesis led to an improvement of the lipotoxic condition. Our data suggest that leptin could be a potent antidiabetic drug in cases of type 2 diabetes that are not leptin resistant.     

Very low-density lipoprotein metabolism in an unusual case of lipoatrophic diabetes

Complete acquired lipoatrophic diabetes (LD) is characterized by nonketotic insulin-resistant diabetes, elevated very low-density lipoprotein (VLDL) triglyceride (TG) levels, and absent subcutaneous fat. We studied a young child in whom LD atypically developed after the onset of type 1 diabetes mellitus. On uncontrolled home diet the patient had triglyceride levels over 1,000 mg/dL on multiple occasions. In order to demonstrate the effects of caloric and dietary-fat restriction on VLDL metabolism, 3H-glycerol and autologous 125I-VLDL were used to quantitate the turnover of VLDL-TG and VLDL-apolipoprotein B (apo B) during two periods of caloric restriction. Consumption of a 900-kcal 40-g fat diet resulted in a plasma triglyceride level of 1383 mg/dL (ten-fold elevation). This hypertriglyceridemia was associated with markedly increased production rates of both VLDL-TG (73.7 mg/kg/h) and VLDL-apo B (126.9 mg/kg/d). Consumption of a 900-kcal 25-g fat diet resulted in a plasma TG level of 663 mg/dL. This reduction in plasma TG was associated with a 40% decrease in VLDL-TG production rate (PR) (45.1 mg/kg/h). There was no change in the production rate (PR) of VLDL-apo B. The hypertriglyceridemia in this patient was due to marked over production of VLDL. Furthermore, the studies demonstrate: (1) the independent benefits of caloric and dietary-fat restriction in the treatment of LD, and (2) that fat restriction lowered plasma triglyceride by its effect on the VLDL-TG production rate.     

Rosiglitazone treatment of patients with extreme insulin resistance and diabetes mellitus due to insulin receptor mutations has no effects on glucose and lipid metabolism

BACKGROUND: Rosiglitazone, a thiazolidinedione (TZD), increases insulin sensitivity by reducing levels of plasma NEFA, triglycerides (TG), glucose and serum insulin. Rosiglitazone treatment decreases insulin resistance in type 2 diabetic patients, but no data exist concerning rosiglitazone treatment of patients with syndromes of extreme insulin resistance. OBJECTIVES: To evaluate whether hyperglycaemia in two lean patients with primary severe insulin resistance due to insulin receptor (IR) mutations and diabetes mellitus could be reduced by supplement of rosiglitazone for 180 days and secondary, to evaluate the effects on plasma NEFA, TG, Apo B, PAI-1 and serum insulin. SUBJECTS: Both patients (brothers) have known mutations in the IR gene localized to the tyrosine kinase domain and a deletion of exon 17 in part of their IR mRNA. Prior to the study the HbA1c values were higher than 10% in both patients for more than 12 months during treatment with insulin and metformin. RESULTS: After 180 days of rosiglitazone supplement (8 mg day(-1)), no changes were observed in fasting plasma glucose and HbA1c. Incremental plasma glucose areas under the curves during a 75-g oral glucose tolerance test (OGTT) were unchanged. Likewise, no improvements were seen in either first or second phase insulin secretion during a 0.3 g kg(-1) intravenous glucose tolerance test (IVGTT). Fasting plasma VLDL and HDL cholesterol, TG and Apo B levels were unchanged, whereas a small increase was seen in total and LDL cholesterol levels. Fasting plasma NEFA increased by 51% in KC after 90 days of treatment, and after 180 days plasma NEFA was still 26% higher, when compared with pretreatment levels. In BC an initial 16% decrease was seen in plasma NEFA after 90 days of treatment. Plasma NEFA was increased 14% after 180 days of treatment, when compared with pretreatment levels, but 35% when compared with day 90. Plasma PAI-1 decreased in both patients after 45 and 90 days of treatment but the decrease was only maintained in KC (47%). CONCLUSIONS: Rosiglitazone treatment, in combination with insulin and metformin, of patients with severe primary insulin resistance due to IR mutations and diabetes mellitus, had no impact on the measured estimates of glucose and lipid metabolism. These findings may suggest that the effect of rosiglitazone on glucose and lipid metabolism are dependent on the presence of intact IR protein.     

Acute hyperglycemia and insulin resistance in acute heart failure syndromes without previously known diabetes

No data is so far available on the relation between glucose values and insulin resistance and mortality, both at short- and long-term, in patients with acute heart failure syndromes (AHF). We prospectively assessed in 100 consecutive non-diabetic AHF patients whether acute glucose metabolism, as indicated by fasting glycemia and insulin resistance (HOMA index) was able to affect short- and long-term mortality. In the overall population, 51 patients showed admission glucose values >140?mg/dl. No significant difference was observed in admission and peak glycemia, insulin and C-peptide values and in HOMA-index between dead and survived patients. At multivariate logistic backward stepwise analysis the following variables were independent predictors for in-ICCU mortality (when adjusted for left ventricular ejection fraction): Fibrinogen (1?mg/dl increase) [OR (95% CI) 0.991 (0.984?C0.997); p?=?0.004]; NT-pro BNP (100?UI increase) [OR (95%CI) 1.005 (1.002?C1.009); p?=?0.004]; leukocyte count (1,000/??l increase) [OR (95%CI) 1.252 (1.070?C1.464); p?=?0.005]. eGFR was independently correlated with long-term mortality (HR 0.96, 95%CI 0.94?C0.98, p?<?0.001). In consecutive patients with acute heart failure without previously known diabetes, we documented, for the first time, that fasting glucose and insulin values and insulin resistance do not affect mortality at short- and long-term. Inflammatory activation (as indicated by the leukocyte count and the fibrinogen) and NT-pro BNP levels are independent predictors for early death while the eGFR affects the long-term mortality.     

Metabolic flexibility in the development of insulin resistance and type 2 diabetes: effects of lifestyle

Lipotoxicity in skeletal muscle plays a critical role in the aetiology of insulin resistance and type 2 diabetes mellitus by interference of lipid metabolites with insulin signalling and action. The dynamics of lipid oxidation and fine tuning with fatty acid uptake and intramyocellular triacylglycerol turnover may be very important to limit the accumulation of lipid intermediates. The use of metabolic inflexibility, defined as the impaired capacity to increase fat oxidation upon increased fatty acid availability and to switch between fat and glucose as the primary fuel source after a meal, does more justice to the complexity of changes in fuel oxidation during the day. Fatty acid availability, uptake and oxidation all play a role in metabolic flexibility and insulin resistance. During high fatty acid availability, fatty acid transporters may limit cellular and mitochondrial fatty acid uptake and thus limit fat oxidation. After a meal, when the demand for fatty acids as fuel is low, an increased fractional extraction of lipids from plasma may promote intramyocellular lipid accumulation and insulin resistance. Furthermore, defects in fuel switching cluster together with impaired mitochondrial content and/or function. Lifestyle changes in dietary fat intake, physical activity and weight loss may improve metabolic flexibility in skeletal muscle, and thereby contribute to the prevention of type 2 diabetes.     

Prospective evaluation of insulin resistance and lipid metabolism in women receiving oral contraceptives

OBJECTIVES It has been suggested that normal women receiving oral contraceptives (OC) may develop a series of metabolic side-effects which relate to the risk of cardiovascular disease. These metabolic disturbances include changes in glucose and insulin metabolism, raised serum lipid and lipoprotein concentrations and elevated blood pressure. All these changes indicate that OC might cause insulin resistance. We have prospectively examined the effect of OC on insulin resistance and lipid metabolism including Lp(a) values. PATIENTS The study group comprised 13 normally menstruating Chinese women. DESIGN The study subjects were given a combined triphasic oral contraceptive which was administered on a 21-day on, 7-day off medication cyclic regimen, the first pill being administered on day 5 from the beginning of menses. The metabolic investigations were carried out during luteal phase before OC and again the third week of the third month of OC administration. MEASUREMENTS Metabolic evaluation including insulin secretion and insulin-mediated glucose uptake were evaluated by oral glucose tolerance test and the modification of insulin suppression test. Fasting triglyceride, cholesterol, HDL-cholesterol and Lp(a) concentrations were also measured. RESULTS The plasma glucose and insulin responses during a 75-g oral glucose challenge increased significantly (P<0 05 and P<003, respectively). The steady-state plasma glucose (SSPG) concentrations achieved during constant infusion of glucose, insulin and somatostatin increased significantly after 3 cycles of OC administration (glucose 7–5±08 vs 124±07 mmol/l, P<0001) while the steady-state plasma insulin (SSPI) concentrations were relatively similar (410±14 vs 391 ±7 pmol/l, NS). Plasma triglyceride levels increased significantly (0 81 ±012 vs 1 09±0 19 mmol/l, P<0 03) following OC administration. Fasting plasma cholesterol, HDL cholesterol and calculated LDL cholesterol concentrations did not change as compared with baseline values, nor did the ratio of total cholesterol to HDL cholesterol. The Lp(a) concentrations did not change during the administration of OC (81 ±25 vs 71 ±21 mg/l, NS). CONCLUSIONS These data indicated that intake of OC for 3 cycles induced glucose intolerance, hyperinsulinaemia and insulin resistance in normal menstruating Chinese women. These changes occurred in association with elevated plasma triglyceride concentrations and no alteration in Lp(a) or other lipid values.     

Lymphatic system changes in diabetes mellitus: role of insulin and hyperglycemia

BACKGROUND: Diabetic alterations of blood vessels have been well studied, but much less is known about the lymphatic system, which plays an important role in the transport of particles and defensive responses. Accordingly, we investigated lymphatic changes in diabetic rats. METHODS: Ten, 30 or 60 days after alloxan-induced diabetes (40 mg/kg; i.v.), we studied thoracic duct lymph flow and lymphocyte output, thoracic duct lymph transport of radiotracer particles ((99m)Tc-dextran 500), lymph node uptake and scintigraphic visualization of subcutaneously injected radiotracer particles, as well as the effect of insulin administration and food deprivation. RESULTS: Diabetes significantly increased thoracic duct lymph flow and the transport of dextran from the footpad subcutaneous tissue. Abnormal lymphocyte output from the thoracic duct occurred in the first 10 days. Uptake of dextran into regional lymph nodes was decreased in diabetes. Insulin per se, although not normalizing blood sugar levels, appeared to recover thoracic duct lymphocyte output and lymph node uptake of (99m)Tc-dextran 500 without affecting the thoracic duct lymph flow or the amount of radiotracer recovered therein. Normalization of glycemia (by food deprivation) restored the lymph flow to control levels without modifying the lymphocyte output. On the other hand, under insulin-restored normoglycemic conditions, both the thoracic duct lymph flow and the lymphocyte output were normalized. CONCLUSIONS: These findings suggest that variables related to defensive mechanisms, such as lymphocyte recirculation and particles uptake into the lymph nodes can benefit from insulin treatment, whereas glycemic control can benefit transport mechanisms in the lymphatic system, such as lymph flow and lymphatic transport of particles.     

Altered expression and function of the insulin receptor in a family with lipoatrophic diabetes

To determine the role of genetic defects in the insulin receptor in the insulin resistance of lipoatrophic diabetes mellitus, we studied insulin binding, insulin receptor autophosphorylation, and insulin receptor mRNA levels and performed Southern blot analysis of genomic DNA in four siblings, all of whom have some degree of insulin resistance and three of whom have lipoatrophy. The insulin receptor concentration in Epstein-Barr virus-transformed lymphocytes was about 30% of normal in all three lipoatrophic siblings (LA1, LA2, and LA3) and was 55% of normal in the nonlipoatrophic sibling (LAS). Insulin receptor mRNA concentrations in the lymphocytes paralleled insulin binding and ranged from 15-67% of the mean normal level. Insulin binding to fibroblasts was also reduced about 50% in the lipoatrophic siblings. In addition, insulin binding to fibroblasts of LAS and LA2 exhibited a rightward shift of the competition curve, suggesting reduced receptor affinity [ED50, 35 and 50 ng/mL (5845 and 8350 pmol/L); normal, 1-3 ng/mL (167-501 pmol/L)]. Receptor autophosphorylation determined using Triton X-100 extracts of the fibroblasts was decreased in LA1 and LA3, but normal in LA2 and LAS. Using restriction enzyme digests of genomic DNA and probes spanning the entire cDNA of the insulin receptor, no gross alterations in receptor gene structure were detected in any members of this family. In 2 of the lipoatrophic siblings (LA1 and LA3) and in the sibling with insulin resistance but no lipoatrophy (LAS), a unique variant BamHI site was detected using a probe to the alpha-subunit region. This site was not found in 200 normal or diabetic insulin receptor alleles. By use of probes 5' and 3' to the alpha-subunit probe and by genomic cloning analysis, this variant BamHI site was localized to an intron in the insulin receptor gene downstream of exon 3 which encodes amino acids 191-296 of the alpha-subunit of the receptor. These data indicate the complex nature of familial lipoatrophic diabetes mellitus, with alterations in insulin receptor expression and/or function in both clinically affected and non-affected siblings. Both the reduced insulin binding and reduced levels of insulin receptor mRNA in the lipoatrophic siblings suggest that an insulin receptor gene defect contributes to this syndrome. Several members of this family also carry a unique variant insulin receptor gene, which, however, could not be linked to a specific alteration in receptor expression or the presence of lipoatrophy.(ABSTRACT TRUNCATED AT 250 WORDS)     

对氧磷酶-1参与调控非酒精性脂肪肝脂质代谢与胰岛素抵抗作用及机制

目的探究对氧磷酶-1(Paraoxonase 1,PON1)与非酒精性脂肪肝(Nonalcoholic fatty liver disease,NAFLD)脂质代谢与胰岛素抵抗关系及机制。方法选取129例NAFLD患者和130非NAFLD患者为研究对象,收集患者年龄、身高、体重、腰围,血压等信息,检测血脂、空腹血糖(Fast Glucose)、胰高血糖素(Glucagon)、胰岛素(Fast Insulin)、评估胰岛素抵抗的稳态指数(homeostatic index of insulin resistance,HOMA-IR)、肝肾功能、脂肪因子等,LO2细胞接种12孔板培养24 h后分别加入0~1.2 mmol OA溶液处理24 h或10 ng/mL TNF-α处理6 h,以PEI转染空载质粒和PON1质粒1μg 24 h。使用尼罗红染料测定细胞内脂质含量。ELISA法检测PON1活性,蛋白质印迹检测PON1、p-IRS1、T-IRS1、p-AKT T-AKT、FAS、HMGCR、SREBP2和SREBP1C蛋白表达。结果NAFLD患者腰围、BMI、外周血ALT、AST、FFA、TG、TC、LDL-C、VLDL-C、空腹血糖、胰岛素、HOMA-IR、抵抗素、瘦素、IL-6和TNF-α显著高于非NAFLD,PON1活性、含量、HDL-C、胰高血糖素和脂联素显著降低;血PON1活性和含量与FFAs、TG、TC、LDL-C、VLDL-C、空腹血糖、胰岛素、HOMA-IR、抵抗素、瘦素、IL-6和TNF-α显著负相关,与HDL-C、胰高血糖素和脂联素显著正相关;OA组LO2细胞PON1的活性逐渐降低,且0.2~1.2 mM OA组LO2细胞PON1的活性显著低于Control组,过表达PON1不影响PON1活性,0.2~1.2 mM OA组LO2细胞内脂质含量显著高于Control组,显著低于OA组;TNF-α组LO2细胞PON1、p-IRS1、p-AKT、FAS、HMGCR、SREBP2和SREBP1C蛋白表达量相比于Control组显著降低,转染PON1质粒显著增加PON1,同时p-IRS1、p-AKT、FAS、HMGCR、SREBP2和SREBP1C蛋白表达量显著增加。结论PON1活性与含量和NAFLD血脂代谢及胰岛素抵抗显著相关,且可能通过调控p-IRS1/AKT通路影响胰岛素抵抗,并调控脂质代谢。     

New insights into insulin resistance pathophysiology: how it affects glucose and lipid metabolism

Insulin resistance is a metabolic state encountered in many physiological and physiopathological conditions. Its pivotal effect on glucose and lipid metabolism is increasingly recognised. Over the last few years, numerous molecular/intracellular pathways affected by this condition have been elucidated. The author reviews some recent findings underlying several major metabolic abnormalities. An overview of current and future therapeutics is also provided.