Can insulin antibodies of diabetic patients distinguish human insulin from porcine insulin?

We examined antisera from patients treated with bovine-porcine mixture (hereafter referred to as bovine/porcine), porcine or human insulin, and compared their binding affinities to human insulin with those to porcine insulin. Patients treated with bovine/porcine insulin developed antisera with a higher affinity to porcine insulin compared with that to human insulin in five of nineteen cases. Furthermore, three of these five antisera had a comparable affinity to bovine and porcine insulin and appeared to recognize the amino acid residue at B-30. Treatment with porcine or human insulin, on the other hand, did not result in any significant difference in the affinity to porcine and human insulin in twenty-three patients. These results indicate the significant role of B-30 amino acid residue as an antigenic determinant, and suggest that the amino acid sequence of the A chain of bovine insulin may contribute to the development of antibody recognizing B-30 amino acid residue.     

Role of miRNAs in the pathogenesis of T2DM,insulin secretion,insulin resistance,and β cell dysfunction: the story so far

Journal of Physiology and Biochemistry - Diabetes, the most common endocrine disorder, also known as a silent killer disease, is characterized by uncontrolled hyperglycemia. According to the...     

Prolonged elevation of insulin content in the unicellular tetrahymena after insulin treatment: induction of insulin production or storage?

In the unicellular organism, Tetrahymena, the first encounter with an exogeneously given hormone results in hormonal imprinting. This causes an increase of the binding capacity of receptors and the production of the appropriate hormone in the progeny generations of the treated cell. In the present experiments the quantity (using radioimmunoassay) and localization (using confocal laser scanning microscopy) of the immunologically insulin‐like material (hereafter insulin) were studied for 10 days after 4 h or 24 h 10⁻⁶ m insulin treatment (hormonal imprinting). Forty‐eight hours after both insulin treatments a high quantity of insulin was present in the cells. This value was also significantly increased after 96 h. After 8 days the difference to the control was significant only in the 24 h treated group. Confocal microscopy (using antibody to pig insulin) localized insulin in the cell body. The oral field contained extremely high quantities of the endogeneous hormone. Insulin treatment (after 48 and 96 h) caused an elevation of insulin content in general, and specific accumulation in the posterior sections of the cell, around the nucleus and in the periphery were observed. Ten days after both treatments only the peripheral region of the cell body and the ciliary row contained more insulin than the control. This means that after insulin treatment the quantity of insulin increases for a lengthy time period which is followed by the expression of insulin in the peripheral region. Insulin contained by Tetrahymena 48 h after imprinting stimulated glucose uptake of rat diaphragm. Copyright © 1999 John Wiley & Sons, Ltd.     

Comparison of pharmacokinetic properties,physicochemical stability,and pump compatibility of 3 rapid-acting insulin analogues— aspart,lispro, and glulisine

ObjectiveTo compare how the rapid-acting insulin analogues (RAIAs) aspart, lispro, and glulisine perform in continuous subcutaneous insulin infusion (CSII) therapy regarding (1) pharmacokinetic properties, (2) chemical and physical stability, and (3) pump compatibility.MethodsPubMed was searched for articles pertaining to the use of RAIAs in CSII, without a restriction on the time period.ResultsThese RAIAs have pharmacokinetic profiles that more closely mimic endogenous insulin in comparison with regular human insulin and tend to produce less hypoglycemia. Among these RAIAs, the rates of absorption and clinical efficacy in terms of glycemic control were similar. Although glulisine showed a faster onset of action in some studies with aspart and lispro, this advantage lasted only for a maximum of 1 hour, after which results were similar for glulisine and aspart or lispro. Each RAIA is created by making minor amino acid substitutions to the regular human insulin molecule and adding a stabilizer to help prevent fibrillation. A series of chemical and covalent changes affecting the primary structure of an insulin preparation, however, may cause decomposition during storage, handling, and use, diminishing the potency of the insulin molecule while contained in an insulin pump. Precipitation, fibrillation, and occlusion may ensue, undermining compatibility for CSII pump use. Aspart has demonstrated the greatest chemical and physical stability in the insulin pump, with the lowest rates of overall occlusion in comparison with lispro and glulisine (aspart 9.2%, lispro 15.7%, and glulisine 40.9%; P < .01).ConclusionAspart is the most compatible of the 3 RAIAs for pump use. (Endocr Pract. 2011;17:271-280)     

A re-interpretation of lipoxygenase-dependent insulin release: which metabolites of arachidonic acid, or none?

There are considerable data implicating a pancreatic islet 12-lipoxy-genase in glucose-induced insulin secretion. This enzyme traditionally is conceived as converting unesterified arachidonic acid to "free" hydroperoxyeicosatetraenoic acid and metabolites thereof. However, studies employing the provision of exogenous metabolites of arachidonic acid to islet tissue fail to identify convincingly the mediator of insulin release. It is proposed that the islet lipoxygenase directly peroxidizes unsaturated fatty acids esterified within membrane phospholipids, leading to changes in ion flux and enzyme activity (particularly phospholipase A2) at the membrane level. The release of unesterified metabolites of arachidonate, although reflecting islet lipoxygenase activity, may be an epiphenomenon.     

Enhanced modelling of the glucose–insulin system and its applications in insulin therapies

It is well known that Michaelis–Menten kinetics is suitable for the response function in chemical reaction, when the reaction rate does not increase indefinitely when an excess of resource is available. However, the existing models for insulin therapies assume that the response function of insulin clearance is proportional to the insulin concentration. In this paper, we propose a new model for insulin therapy for both type 1 and type 2 diabetes mellitus, in which the insulin degradation rate assumes Michaelis–Menten kinetics. Our analysis shows that it is possible to mimic pancreatic insulin secretion by exogenous insulin infusions, and our numerical simulations provide clinical strategies for insulin–administration practices.     

Maintenance of the postabsorptive plasma glucose concentration: insulin or insulin plus glucagon?

The prevalent view is that the postabsorptive plasma glucose concentration is maintained within the physiological range by the interplay of the glucose-lowering action of insulin and the glucose-raising action of glucagon. It is supported by a body of evidence derived from studies of suppression of glucagon (and insulin, among other effects) with somatostatin in animals and humans, immunoneutralization of glucagon, defective glucagon synthesis, diverse mutations, and absent or reduced glucagon receptors in animals and glucagon antagonists in cells, animals, and humans. Many of these studies are open to alternative interpretations, and some lead to seemingly contradictory conclusions. For example, immunoneutralization of glucagon lowered plasma glucose concentrations in rabbits, but administration of a glucagon antagonist did not lower plasma glucose concentrations in healthy humans. Evidence that the glycemic threshold for glucagon secretion, unlike that for insulin secretion, lies below the physiological range, and the finding that selective suppression of insulin secretion without stimulation of glucagon secretion raises fasting plasma glucose concentrations in humans underscore the primacy of insulin in the regulation of the postabsorptive plasma glucose concentration and challenge the prevalent view. The alternative view is that the postabsorptive plasma glucose concentration is maintained within the physiological range by insulin alone, specifically regulated increments and decrements in insulin, and the resulting decrements and increments in endogenous glucose production, respectively, and glucagon becomes relevant only when glucose levels drift below the physiological range. Although the balance of evidence suggests that glucagon is involved in the maintenance of euglycemia, more definitive evidence is needed, particularly in humans.     

How α-crystallin prevents the aggregation of insulin

Using steady-state, polarized, and phase-modulation fluorometry, the dithiothreitol-induced denaturation of insulin and formation of its complex with alpha-crystallin in solution were studied. Prevention of the aggregation of insulin by alpha-crystallin is due to formation of chaperone complexes, i.e. interaction of chains of the denatured insulin with alpha-crystallin. The conformational changes in alpha-crystallin that occur during complex formation are rather small. It is unlikely that N-termini are directly involved in the complex formation. The 8-anilino-1-naphthalenesulfonate (ANS) is not sensitive to the complex formation. ANS emits mainly from alpha-crystallin monomers, dimers, and tetramers, but not from oligomers or aggregates. The possibility of highly sensitive detection of aggregates by light scattering using a spectrofluorometer with crossed monochromators is demonstrated.     

Is the insulin resistance of patients with noninsulin-dependent diabetes mellitus secondary to insulin deficiency?

Defects in both insulin secretion and action have been documented in patients with noninsulin-dependent diabetes mellitus (NIDDM), leading to the suggestion that both fasting hyperglycemia and insulin resistance in NIDDM are secondary to insulin deficiency. In order to test this hypothesis, insulin secretion (plasma insulin response to oral glucose) and insulin action (insulin clamp) were determined in 25 patients with NIDDM. The results documented relationships between incremental plasma insulin response to glucose and degree of fasting hyperglycemia (r = -.045, P less than 0.05) and insulin-stimulated glucose utilization (r = 0.25, P = NS). These data indicate that differences in insulin secretory response accounted for only approximately 20% of the variance in fasting plasma glucose level and 6% of the variance in insulin resistance in NIDDM. Thus, differences in insulin-secretory response contribute modestly to magnitude of glycemia, and not at all to variations in insulin resistance in NIDDM, permitting rejection of the hypothesis that insulin resistance is secondary to insulin deficiency.     

Secretory expression of α single-chain insulin precursor in yeast and its conversion into human insulin

A synthetic single-chain porcine insulin precursor (PIP) gene and an α-mating factor leader sequence (αMFL) gene obtained by the PCR method are inserted between the promoter and 3'-terminating sequence of the alcohol dehydrogenase gene ADH1 in plasmid pVT102-U to form plasmid pVT102-U/α MFL-PIP. The single-chain insulin precursor is expressed and secreted to the culture medium by Saccharomyces cererisiae transformed by pVT102-U/αMFL-PIP. The precursor is purified and converted into human insulin by tryptic transpeptidation. The purified human insulin is fully active and can be crystallized. The overall yield of human insulin is 25 mg per liter of culture medium.     

Effect of leptin on insulin resistance of muscle--direct or indirect?

We examined the effect of leptin on the insulin resistance in skeletal muscles by measuring glucose transport. Male Wistar rats were fed rat chow or high-fat diets for 30 days. Before sacrifice, rats fed high-fat diet were subcutaneously injected with leptin (1 mg/kg b.w.) for 3 days. The glucose transport in epitrochlearis and soleus muscles did not differ in the experimental groups under basal conditions, however these values decreased significantly in the rats fed high-fat diet under insulin stimulation (p<0.01). Leptin treatment recovered the decreased glucose transport in epitrochlearis (p<0.05) and soleus muscles (p=0.08). Triglyceride concentrations in soleus muscles were increased significantly in the rats fed high-fat diet as compared to rats fed chow diet (p<0.01), and were decreased significantly by leptin treatment (p<0.01). The glucose transport was measured under basal conditions and after 60 microU/ml of insulin treatment with or without 50 ng/ml of leptin. Leptin had no direct stimulatory effect on glucose transport under both basal and insulin-stimulated conditions in vitro. These results demonstrate that leptin injection to rats fed high-fat diet recovered impaired insulin responsiveness of skeletal muscles and muscle triglyceride concentrations. However, there was no direct stimulatory effect of leptin on insulin sensitivity of skeletal muscles in vitro.     

The pancreatic β-cell recognition of insulin secretagogues. Effects of calcium and sodium on glucose metabolism and insulin release

The transport and oxidation of glucose, the content of fructose 1,6-diphosphate, and the release of insulin were studied in microdissected pancreatic islets of ob/ob mice incubated in Krebs-Ringer bicarbonate medium. Under control conditions glucose oxidation and insulin release showed a similar dependence on glucose concentration with the steepest slope in the range 5-12mm. The omission of Ca(2+), or the substitution of choline ions for Na(+), or the addition of diazoxide had little if any effect on glucose transport. However, Ca(2+) or Na(+) deficiency as well as diazoxide (7-chloro-3-methyl-1,2,4-benzothiadiazine 1,1-dioxide) or ouabain partially inhibited glucose oxidation. These alterations of medium composition also increased the islet content of fructose 1,6-diphosphate, as did the addition of adrenaline. Phentolamine [2-N-(3-hydroxyphenyl)-p-toluidinomethyl-2-imidazoline] counteracted the effects of adrenaline and Ca(2+) deficiency on islet fructose 1,6-diphosphate. After equilibration in Na(+)-deficient medium, the islets exhibited an increase in basal insulin release whereas the secretory response to glucose was inhibited. The inhibitory effects of Na(+) deficiency on the secretory responses to different concentrations of glucose correlated with those on (14)CO(2) production. When islets were incubated with 17mm-glucose, the sudden replacement of Na(+) by choline ions resulted in a marked but transient stimulation of insulin release that was not accompanied by a demonstrable increase of glucose oxidation. Galactose and 3-O-methylglucose had no effect on glucose oxidation or on insulin release. The results are consistent with a metabolic model of the beta-cell recognition of glucose as insulin secretagogue and with the assumption that Ca(2+) or Na(+) deficiency, or the addition of adrenaline or diazoxide, inhibit insulin release at some step distal to stimulus recognition. In addition the results suggest that these conditions create a partial metabolic block of glycolysis in the beta-cells. Hence the interrelationship between the processes of stimulus recognition and insulin discharge may involve a positive feedback of secretion on glucose metabolism.     

Modulation of islet G-proteins, α-glucosidehydrolase inhibition and insulin release stimulated by various secretagogues

Guanine nucleotide-binding proteins (G-proteins) are known to act as important modulators of insulin release from the islets of Langerhans. We have recently found that the deoxynojirimycin-derivative emiglitate, a recognized inhibitor of intestinal -glucosidehydrolase activity, is a powerful inhibitor of glucose-induced insulin release. With the use of isolated mouse islets the present investigation was performed in a primary attempt to elucidate whether this inhibitory mechanism in some way was linked to the -cell G-protein system. Treatment of freshly isolated islets with pertussis toxin (PTX), which is known to inactivate the G_i-proteins, abolished the inhibitory effect of the ₂-adrenoceptor agonist clonidine on insulin release stimulated by the phosphodiesterase inhibitor IBMX in the presence of the protein kinase C activator TPA and even changed it into an increase. Emiglitate did not display any inhibitory action on insulin release induced by these secretagogues. Similarly, clonidine-induced inhibition of glucose stimulated insulin release was reversed by PTX. However, PTX did not influence the suppressive action of emiglitate on glucose-induced insulin secretion. In contrast, the adenylate cyclase activator forskolin totally abolished the inhibitory effect of emiglitate, but not that of the glucose analogue mannoheptulose, on glucose-induced insulin release. Moreover, the stimulatory effect of forskolin and cholera toxin (CTX) (activator of G_s-proteins) on the secretion of insulin was markedly enhanced in the presence of emiglitate. In conclusion, our results suggest that the inhibitory effect of emiglitate on glucose-induced insulin release is not directly related to the G_j-proteins, but most likely exerted solely through the selective suppression of lysosomal -glucosidehydrolase activity, a step in between the proximal and the distal G_i-proteins, in glucose-induced stimulus-secretion mechanisms. Our data also suggests that the inhibitory action of emiglitate on glucose stimulated insulin release can be compensated for by an increased sensitivity of the cyclic AMP-protein kinase A pathway. Hence, emiglitate might indirectly elicit an increased activity of the G_s-proteins to facilitate the secretory process.     

Insulin secretion: Feed-forward control of insulin biosynthesis?

It has long been accepted wisdom that insulin secreted from islet beta cells has either no effect, or an inhibitory feedback effect, on insulin synthesis and secretion. Recent work suggests, instead, that secreted insulin acts directly on beta cells, via its own receptor, to enhance insulin production in an autocrine feed-forward loop.     

Interacting epidemics? Sleep curtailment, insulin resistance, and obesity

In the last 50 years, the average self-reported sleep duration in the United States has decreased by 1.5-2 hours in parallel with an increasing prevalence of obesity and diabetes. Epidemiological studies and meta-analyses report a strong relationship between short or disturbed sleep, obesity, and abnormalities in glucose metabolism. This relationship is likely to be bidirectional and causal in nature, but many aspects remain to be elucidated. Sleep and the internal circadian clock influence a host of endocrine parameters. Sleep curtailment in humans alters multiple metabolic pathways, leading to more insulin resistance, possibly decreased energy expenditure, increased appetite, and immunological changes. On the other hand, psychological, endocrine, and anatomical abnormalities in individuals with obesity and/or diabetes can interfere with sleep duration and quality, thus creating a vicious cycle. In this review, we address mechanisms linking sleep with metabolism, highlight the need for studies conducted in real-life settings, and explore therapeutic interventions to improve sleep, with a potential beneficial effect on obesity and its comorbidities.