OBJECTIVE -Glycemic control using inhaled, dry-powder insulin plus a single injection of long-acting insulin was compared with a conventional regimen in patients with type 2 diabetes, which was previously managed with at least two daily insulin injections.RESEARCH DESIGN AND METHODS -Patients were randomized to 6 months' treatment with either premeal inhaled insulin plus a bedtime dose of Ultralente (n ϭ 149) or at least two daily injections of subcutaneous insulin (mixed regular/NPH insulin; n ϭ 150). The primary efficacy end point was the change in HbA 1c from baseline to the end of study.RESULTS -HbA 1c decreased similarly in the inhaled (Ϫ0.7%) and subcutaneous (Ϫ0.6%) insulin groups (adjusted treatment group difference: Ϫ0.07%, 95% CI Ϫ0.32 to 0.17). HbA 1c Ͻ7.0% was achieved in more patients receiving inhaled (46.9%) than subcutaneous (31.7%) insulin (odds ratio 2.27, 95% CI 1.24 -4.14). Overall hypoglycemia (events per subject-month) was slightly lower in the inhaled (1.4 events) than in the subcutaneous (1.6 events) insulin group (risk ratio 0.89, 95% CI 0.82-0.97), with no difference in severe events. Other adverse events, with the exception of increased cough in the inhaled insulin group, were similar. No difference in pulmonary function testing was seen. Further studies are underway to assess tolerability in the longer term. Insulin antibody binding increased more in the inhaled insulin group. Treatment satisfaction was greater in the inhaled insulin group.CONCLUSIONS -Inhaled insulin appears to be effective, well tolerated, and well accepted in patients with type 2 diabetes and provides glycemic control comparable to a conventional subcutaneous regimen.

Glucokinase, a key regulatory enzyme of glucose metabolism in mammals, provides an interesting model of tissue-specific gene expression. The single-copy gene is expressed principally in liver, where it gives rise to a 2.4-kilobase mRNA. The islets of Langerhans of the pancreas also contain glucokinase. Using a cDNA complementary to rat liver glucokinase mRNA, we show that normal pancreatic islets and tumoral islet cells contain a glucokinase mRNA species -400 nucleotides longer than hepatic mRNA. Hybridization with synthetic oligonucleotides and primer-extension analysis show that the liver and islet glucokinase mRNAs differ in the 5' region. Glucokinase mRNA is absent from the livers of fasted rats and is strongly induced within hours by an oral glucose load. In contrast, islet glucokinase mRNA is expressed at a constant level during the fasting-refeeding cycle. The level of glucokinase protein in islets measured by immunoblotting is unaffected by fasting and refeeding, whereas a 3-fold increase in the amount of enzyme occurs in liver during the transition from fasting to refeeding. From these data, we conclude (i) that alternative splicing and/or the use of distinct tissue-specific promoters generate structurally distinct mRNA species in liver and islets of Langerhans and (ii) that tissue-specific transcription mechanisms result in inducible expression of the glucokinase gene in liver but not in islets during the fasting-refeeding transition.Glucokinase is one of the isoenzymes of the mammalian hexokinase group (ATP:D-hexose-6-phosphotransferase, EC 2.7.1.1). It has attracted considerable interest because of its distinctive structural and catalytic properties, as well as its typical tissue distribution (1, 2). Glucokinase activity is found only in liver and in the islets of Langerhans of the pancreas. Glucokinases of liver and pancreatic islets display similar chromatographic and electrophoretic behavior, suggesting that the enzyme from both tissues is the product of a single or two closely related genes (3, 4). In liver, glucokinase is considered to play a key regulatory role in glucose uptake and release (5). In the islets of Langerhans, it has been ascribed the role ofglucose sensor in the regulation of insulin secretion (6). Further interest in this enzyme arises from its multihormonal regulation in liver (7,8). In particular, it has been shown (9) that insulin rapidly stimulates transcription of the glucokinase gene in the liver of the diabetic rat. Virtually nothing is known, however, about a possible influence of nutritional or hormonal factors on glucokinase gene expression in pancreatic islets. Moreover, the mechanisms underlying the restricted tissue distribution ofglucokinase have not been investigated at the molecular level. The cloning of cDNA for hepatic glucokinase (10) has allowed us to address these issues directly. The findings reported herein provide insight into the tissue-specific expression and regulation of the gene encoding this important enzyme of carbohydrate metabolism. MATER...

Expression of peroxisome proliferatoractivated receptor ␣ (PPAR␣) and enzymes of fatty acid (FA) oxidation is markedly reduced in the fat-laden, dysfunctional islets of obese, prediabetic Zucker diabetic fatty ( fa͞fa) rats with mutated leptin receptors (OB-R). Leptin, PPAR␣͞ retinoid x receptor ligands, and FA all up-regulate PPAR␣ and enzymes of FA oxidation and stimulate [ 3 H]-palmitate oxidation in normal islets but not in islets from fa͞fa rats. Overexpression of normal OB-R in islets of fa͞fa rats corrects all of the foregoing abnormalities and reverses the diabetic phenotype. PPAR␣ is a OB-R-dependent factor required for normal fat homeostasis in islet cells.

To elucidate the mechanism of the basal hyperinsulinemia of obesity, we perfused pancreata from obese Zucker and lean Wistar rats with substimulatory concentrations of glucose. Insulin secretion at 4.2 and 5.6 mM glucose was approximately 10 times that of controls, whereas beta-cell volume fraction was increased only 4-fold and DNA per islet 3.5-fold. We therefore compared glucose usage at 1.4, 2.8, and 5.6 mM. Usage was 8-11.4 times greater in Zucker islets at 1.4 and 2.8 mM and 4 times greater at 5.6 mM; glucose oxidation at 2.8 and 5.6 mM glucose was > 12 times lean controls. To determine if the high free fatty acid (FFA) levels of obesity induce these abnormalities, normal Wistar islets were cultured with 0, 1, or 2 mM long chain FFA for 7 days. Compared to islets cultured without FFA insulin secretion by FFA-cultured islets (2 mM) perifused with 1.4, 3, or 5.6 mM glucose was increased more than 2-fold, bromodeoxyuridine incorporation was increased 3-fold, and glucose usage at 2.8 and 5.6 mM glucose was increased approximately 2-fold (1 mM FFA) and 3-fold (2 mM FFA). We conclude that hypersecretion of insulin by islets of obese Zucker fatty rats is associated with, and probably caused by, enhanced low Km glucose metabolism and beta-cell hyperplasia, abnormalities that can be induced in normal islets by increased FFA.

Amyloid deposits in the islets of Langerhans of the pancreas are a common finding in non-insulin-dependent diabetes mellitus. The main protein constituent of these deposits is a 37-amino acid peptide known as amylin that resembles calcitonin gene-related peptide, a neuropeptide. We have isolated cDNA clones corresponding to the rat amylin precursor from an islet cDNA library and we show that this peptide is encoded in a 0.9-kilobase mRNA that is translated to yield a 93-amino acid precursor. The amylin peptide is bordered by dibasic residues, suggesting that it is proteolyzed like calcitonin gene-related peptide. The peptide sequences flanking the amylin sequence do not resemble the calcitonin gene-related peptide flanking sequences. RNA hybridization studies show that amylin mRNA is abundant in the islets of Langerhans but is not present in the brain or seven other tissues examined. Dietary changes, such as fasting or fasting and refeeding, have little effect on amylin mRNA expression. This tissue specificity suggests that amylin is involved in specific signaling pathways related to islet function. levels and glucose-stimulated insulin secretion (13). Leighton and Cooper (14) found that CGRP inhibits insulin-stimulated glycogen synthesis in skeletal muscle, although it did not affect glycolysis. A comparable inhibition was observed using amylin purified from the pancreas of diabetic patients or synthetic amylin (14,15). No effect was seen in adipose tissue. These studies suggest that amylin may affect insulin secretion and the sensitivity of peripheral tissues to insulin.To define the primary structure of amylin in the islets, we have isolated and characterized cDNAs encoding rat amylin from an islet cDNA library.l Sequence analysis shows that a 0.9-kilobase mRNA encodes a 93-amino acid precursor that is proteolyzed to yield the final amylin product. RNA expression studies show that this molecule is expressed at high levels in the islets of Langerhans of normal animals but is not detected in the brain or any of seven other tissues in the rat. Amylin thus appears to be a normal constituent of the / cell that is processed in a fashion similar to other peptide hormones and is secreted with insulin from the islet.The pancreas ofpatients with non-insulin-dependent diabetes mellitus (NIDDM) contains deposits of amyloid, an extracellular protein matrix with unique staining characteristics (1-4). Small deposits of amyloid are also found in the pancreas of an elderly patient without diabetes; however, in patients with NIDDM they occur earlier and are more widespread. Cooper and coworkers (5, 6) and Westermark et al. (7,8) have purified and sequenced the peptide that is the major component of islet amyloid in NIDDM. This peptide, known as amylin, diabetes-associated peptide (DAP), or islet amyloid polypeptide (IAPP), is a 37-amino acid peptide that is 50% identical to calcitonin gene-related peptide (CGRP). Johnson et al. (9) have found amylin immunoreactive material in normal islets within insulin-containing s...