Insulin therapy or intensification of insulin therapy commonly results in weight gain in both type 1 and type 2 diabetes. This weight gain can be excessive, adversely affecting cardiovascular risk profile. The spectre of weight gain can increase diabetic morbidity and mortality when it acts as a psychological barrier to the initiation or intensification of insulin, or affects adherence with prescribed regimens. Insulin-associated weight gain may result from a reduction of blood glucose to levels below the renal threshold without a compensatory reduction in calorie intake, a defensive or unconscious increase in calorie intake caused by the fear or experience of hypoglycaemia, or the 'unphysiological' pharmacokinetic and metabolic profiles that follow subcutaneous administration. There is, however, scope for limiting insulin-associated weight gain. Strategies include limiting dose by increasing insulin sensitivity through diet and exercise or by using adjunctive anorectic or insulin-sparing pharmacotherapies such as pramlintide or metformin. Insulin replacement regimens that attempt to mimic physiological norms should also enable insulin to be dosed with maximum efficiency. The novel acylated analogue, insulin detemir, appears to lack the usual propensity for causing weight gain. Elucidation of the pharmacological mechanisms underlying this property might help clarify the mechanisms linking insulin with weight regulation.

Insulin‐associated weight gain in diabetes – causes, effects and coping strategies

OBJECTIVE —To assess the efficacy and safety of initial combination therapy with sitagliptin and metformin in patients with type 2 diabetes and inadequate glycemic control on diet and exercise.

RESEARCH DESIGN AND METHODS —In a 24-week, randomized, double-blind, placebo-controlled, parallel-group study, 1,091 patients with type 2 diabetes and A1C 7.5–11% were randomized to one of six daily treatments: sitagliptin 100 mg/metformin 1,000 mg (S100/M1000 group), sitagliptin 100 mg/metformin 2,000 mg (S100/M2000 group), metformin 1,000 mg (M1000 group), metformin 2,000 mg (M2000 group) (all as divided doses administered twice daily [b.i.d.]), sitagliptin 100 mg q.d. (S100 group), or placebo. Patients who had an A1C >11% or a fasting glucose value >280 mg/dl after the run-in period were not eligible to be randomized; these patients could participate in an open-label substudy and were treated with S100/M2000 for 24 weeks.

RESULTS —The mean baseline A1C was 8.8% in the randomized patients. The placebo-subtracted A1C change from baseline was −2.07% (S100/M2000), −1.57% (S100/M1000), −1.30% (M2000), −0.99% (M1000), and −0.83% (S100) ( P < 0.001 for comparisons versus placebo and for coadministration versus respective monotherapies). The proportion of patients achieving an A1C <7% and <6.5% was 66 and 44%, respectively, in the S100/M2000 group ( P < 0.001 vs. S100 or M2000). For the open-label cohort ( n = 117; baseline A1C 11.2%) treated with S100/M2000, the within-group mean A1C change from baseline was −2.9%. The incidence of hypoglycemia was low (0.5–2.2%) across active treatment groups and not significantly different from that in the placebo group (0.6%). The incidence of gastrointestinal adverse experiences was similar for coadministration therapies compared with their respective metformin monotherapy.

CONCLUSIONS —The initial combination of sitagliptin and metformin provided substantial and additive glycemic improvement and was generally well tolerated in patients with type 2 diabetes.

https://care.diabetesjournals.org/content/diacare/30/8/1979.full.pdf

Effect of Initial Combination Therapy With Sitagliptin, a Dipeptidyl Peptidase-4 Inhibitor, and Metformin on Glycemic Control in Patients With Type 2 Diabetes

OBJECTIVE Recent studies suggest the beneficial effects of metformin on glucose metabolism may be microbially mediated. We examined the association of type 2 diabetes, metformin, and gut microbiota in community-dwelling Colombian adults. On the basis of previous research, we hypothesized that metformin is associated with higher levels of short-chain fatty acid (SCFA)–producing and mucin-degrading microbiota. RESEARCH DESIGN AND METHODS Participants were selected from a larger cohort of 459 participants. The present analyses focus on the 28 participants diagnosed with diabetes—14 taking metformin— and the 84 participants without diabetes who were matched (3-to-1) to participants with diabetes by sex, age, and BMI. We measured demographic information, anthropometry, and blood biochemical parameters and collected fecal samples from which we performed 16S rRNA gene sequencing to analyze the composition and structure of the gut microbiota. RESULTS We found an association between diabetes and gut microbiota that was modified by metformin use. Compared with participants without diabetes, participants with diabetes taking metformin had higher relative abundance of Akkermansia muciniphila, a microbiota known for mucin degradation, and several gut microbiota known for production of SCFAs, including Butyrivibrio, Bifidobacterium bifidum, Megasphaera, and an operational taxonomic unit of Prevotella. In contrast, compared with participants without diabetes, participants with diabetes not taking metformin had higher relative abundance of Clostridiaceae 02d06 and a distinct operational taxonomic unit of Prevotella and a lower abundance of Enterococcus casseliflavus. CONCLUSIONS Our results support the hypothesis that metformin shifts gut microbiota composition through the enrichment of mucin-degrading A. muciniphila as well as several SCFA-producing microbiota. Future studies are needed to determine if these shifts mediate metformin’s glycemic and anti-inflammatory properties.

/pdf/metformin-is-associated-with-higher-relative-abundance-of-4vn9zlwk5p.pdf

Metformin Is Associated With Higher Relative Abundance of Mucin-Degrading Akkermansia muciniphila and Several Short-Chain Fatty Acid-Producing Microbiota in the Gut.

The management of T2DM requires aggressive treatment to achieve glycemic and cardiovascular risk factor goals. In this setting, metformin, an old and widely accepted first line agent, stands out not only for its antihyperglycemic properties but also for its effects beyond glycemic control such as improvements in endothelial dysfunction, hemostasis and oxidative stress, insulin resistance, lipid profiles, and fat redistribution. These properties may have contributed to the decrease of adverse cardiovascular outcomes otherwise not attributable to metformin’s mere antihyperglycemic effects. Several other classes of oral antidiabetic agents have been recently launched, introducing the need to evaluate the role of metformin as initial therapy and in combination with these newer drugs. There is increasing evidence from in vivo and in vitro studies supporting its anti-proliferative role in cancer and possibly a neuroprotective effect. Metformin’s negligible risk of hypoglycemia in monotherapy and few drug interactions of clinical relevance give this drug a high safety profile. The tolerability of metformin may be improved by using an appropiate dose titration, starting with low doses, so that side-effects can be minimized or by switching to an extended release form. We reviewed the role of metformin in the treatment of patients with type 2 diabetes and describe the additional benefits beyond its glycemic effect. We also discuss its potential role for a variety of insulin resistant and pre-diabetic states, obesity, metabolic abnormalities associated with HIV disease, gestational diabetes, cancer, and neuroprotection.

/pdf/metformin-an-old-but-still-the-best-treatment-for-type-2-44270g0l1q.pdf

Metformin: an old but still the best treatment for type 2 diabetes

Metformin is an effective agent with a good safety profile that is widely used as a first-line treatment for type 2 diabetes, yet its mechanisms of action and variability in terms of efficacy and side effects remain poorly understood. Although the liver is recognised as a major site of metformin pharmacodynamics, recent evidence also implicates the gut as an important site of action. Metformin has a number of actions within the gut. It increases intestinal glucose uptake and lactate production, increases GLP-1 concentrations and the bile acid pool within the intestine, and alters the microbiome. A novel delayed-release preparation of metformin has recently been shown to improve glycaemic control to a similar extent to immediate-release metformin, but with less systemic exposure. We believe that metformin response and tolerance is intrinsically linked with the gut. This review examines the passage of metformin through the gut, and how this can affect the efficacy of metformin treatment in the individual, and contribute to the side effects associated with metformin intolerance.

/pdf/metformin-and-the-gastrointestinal-tract-1w0ojsoagk.pdf

Metformin and the gastrointestinal tract.

OBJECTIVE —To evaluate the effects of metformin on glucagon-like peptide 1 (GLP-1) and leptin levels. RESEARCH DESIGN AND METHODS —A total of 10 obese nondiabetic male patients were studied before and after a 14-day treatment with 2,550 mg/day metformin and were compared with 10 untreated obese control subjects. On days 0 and 15, leptin and GLP-1(7–36)amide/(7–37) levels were assessed before and after an oral glucose load during a euglycemic hyperinsulinemic clamp to avoid the interference of variations of insulinemia and glycemia on GLP-1 and leptin secretion. The effects of metformin on GLP-1(7–36)amide degradation in human plasma and in a buffer solution containing dipeptidyl peptidase IV (DPP-IV) were also studied. RESULTS —Leptin levels were not affected by the oral glucose load, and they were not modified after metformin treatment. Metformin induced a significant ( P CONCLUSIONS —Metformin significantly increases GLP-1 levels after an oral glucose load in obese nondiabetic subjects; this effect could be due to an inhibition of GLP-1 degradation.

https://care.diabetesjournals.org/content/diacare/24/3/489.full.pdf

Enrica Pierazzuoli

Papers

Effect of Metformin on Glucagon-Like Peptide 1 (GLP-1) and Leptin Levels in Obese Nondiabetic Subjects