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\begin{document}

\title{Acute effect of add-on therapy with tofogliflozin, a sodium glucose
co-transporter 2 inhibitor, on 24-hour glucose profile and glycemic
variability evaluated by continuous glucose monitoring in patients with
type 2 diabetes receiving dipeptidyl peptidase-4 inhibitors.}



\author[1]{Yoshimasa Aso}%
\author[1]{Toshie Iijima}%
\author[2]{Soichiro Hosonuma}%
\author[2]{Hidetaka Kurai}%
\author[2]{Hayato Kanitani}%
\author[2]{Shintaro Sakurai}%
\author[2]{Takuya Tomaru}%
\author[2]{Teruo Jojima}%
\author[2]{Isao Usui}%
\affil[1]{Dokkyo Medical University}%
\affil[2]{Affiliation not available}%


\vspace{-1em}



  
  \date{May 24, 2024}


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\selectlanguage{english}
\begin{abstract}
Aim: To investigate acute effects of add-on therapy with the sodium
glucose co-transporter 2 inhibitor tofogliflozin to dipeptidyl peptidase
(DPP)-4 inhibitors on 24-hour glucose profile and glycemic variability
evaluated by continuous glucose monitoring (CGM) in patients with type 2
diabetes. Patients and methods: We studied 17 patients with type 2
diabetes who were hospitalized for glycemic control. CGM was performed
for 7 consecutive days in the last week of hospitalization.
Tofogliflozin 20 mg/day was started on day 4 after initiating CGM and
was administered to 10 patients receiving DPP-4 inhibitors and 7
patients not receiving DPP-4 inhibitors. We compared several CGM
parameters between day 2 to 3 (ie, before treatment with tofogliflozin)
and day 5 to 6 (ie, after starting treatment with tofogliflozin).
Results: After starting treatment with tofogliflozin, mean 24-hour
glucose and postprandial glucose after each meal were significantly
decreased in both groups of patients. Time in range (ie, at a glucose
level of 70-180 mg/dL) was significantly increased in both groups. The
standard deviation of 24-hour glucose and mean amplitude of glycemic
excursions, 2 indexes of glycemic variability, were significantly
decreased in patients receiving DPP-4 inhibitors but were unchanged in
those not receiving these drugs. Conclusions: Add-on therapy with
tofogliflozin to DPP-4 inhibitors acutely reduces 24-hour glucose levels
and improves glycemic variability in patients with type 2 diabetes.%
\end{abstract}%



\sloppy


\textbf{Introduction}

Sodium glucose co-transporter 2 (SGLT2) inhibitors improve glycemic
control in people with type 2 diabetes by increasing urinary glucose
excretion; additional benefits are body weight loss and a low risk of
hypoglycemia (1). Furthermore, several large-scale clinical trials of
SGLT2 inhibitors have shown that these drugs have beneficial effects on
cardiovascular outcomes---including hospitalization for heart failure
and cardiovascular death---and renal outcomes in high-risk patients and
that these effects appear to be independent of the glucose-lowering
efficacy of these drugs (2-4).

SGLT2 inhibitors have been reported to increase plasma glucagon
concentration and endogenous glucose production (EGP) in patients with
type 2 diabetes (5, 6). Ferrannini et al demonstrated that acute dosing
(ie, a single tablet) of empagliflozin, an SGLT2 inhibitor, increases
both fasting and postprandial rates of EGP in patients with type 2
diabetes (5). The increase in EGP after treatment with SGLT2 inhibitors
may be attributed partly to an elevated plasma glucagon level. The
reduction in plasma glucose concentration expected with SGLT2 inhibitors
may be partially offset by a concomitant increase in EGP through a
compensatory mechanism caused by declining blood glucose or glucosuria
(5, 6).

In contrast, dipeptidyl peptidase (DPP)-4 inhibitors, incretin-based
drugs, suppress EGP by stimulating insulin secretion and inhibiting
glucagon secretion by enhancing glucagon-like peptide-1 (GLP-1) (7, 8).
DPP-4 inhibitors may antagonize the compensatory increase in EGP induced
by SGLT2 inhibitors. Therefore, we hypothesized that the increase in EGP
after administration of SGLT2 inhibitors may be attenuated in patients
receiving DPP-4 inhibitors and that, consequently, the glucose-lowering
effects of SGLT2 inhibitors may be stronger in patients receiving DPP-4
inhibitors than in those not receiving them. To study this hypothesis,
we investigated the acute effect of addition of tofogliflozin, an SGLT2
inhibitor, on 24-hour glucose levels and glycemic variability evaluated
by continuous glucose monitoring (CGM) in patients with type 2 diabetes
receiving or not receiving DPP-4 inhibitors.

\textbf{Subjects and Methods}

We studied 17 patients with type 2 diabetes who were hospitalized for
glycemic control at the Dokkyo Medical University Hospital (Mibu,
Tochigi, Japan). Patients were eligible for enrollment if they had type
2 diabetes, were at least 20 years old and had a glycated hemoglobin
(HbA1c) level of 6.0\% to 12.0\% on stable therapy with 1 to 3 oral
antidiabetic drugs with or without insulin for at least 3 months. During
hospitalization, all patients received an optimal diet therapy (25 to 30
kcal/kg of ideal body weight; 50\% carbohydrate, 20\% protein, and 30\%
fat). Tofogliflozin 20 mg/day was administered to 10 patients who were
receiving DPP-4 inhibitors and to 7 patients who were not receiving
these drugs.

During the last week of hospitalization, a CGM device (iPro2; Medtronic
MiniMed. Inc., Northridge, CA, USA) was attached to each patient for 1
week. During the study period, no other anti-diabetic drugs were added
and the dose of antidiabetic drugs and insulin remained unchanged. The
starting day of CGM was defined as day 1. On day 4, treatment with
tofogliflozin 20 mg/day was started. We compared the mean values of CGM
parameters on day 2 and 3 (ie, before starting treatment with
tofogliflozin) with those on day 5 and 6 (ie, after staring treatment
with tofogliflozin). As indexes of glycemic variability, the 24-hour
mean glucose level, standard deviation (SD) of the 24-hour glucose
level, mean amplitude of glycemic excursions (MAGE), and mean of
postprandial glucose excursion (MPPGE) were calculated from CGM. We
evaluated postprandial glucose within 1 to 3 hours after each meal and
the time in range as the percent time with a glucose level between 70
and 180~mg/dL. Time below range was defined as the percent of time with
a glucose level less than 70 mg/dL, and time above range, as the percent
of time with a glucose level above 180 mg/dL.

All participants gave written informed consent to participate in the
study, which was approved by the Institutional Review Board of Dokkyo
Medical University (approval no. 28150). The study was registered with
the University Hospital Medical Information Network Clinical Trials
Registry (UMIN000025454).

\textbf{Statistical analysis}

Results were expressed as the mean (SD) or the median and interquartile
range. Differences between groups were analyzed by Student's
paired\emph{t} test or unpaired \emph{t} test, and differences in
nonparametric data were assessed by Wilcoxon's matched-pairs test or the
Mann-Whitney U test. A \emph{P} value of less than 0.05 was considered
statistically significant.

\textbf{Results}

As shown in Table 1, the overall characteristics of the two groups of
patients were well matched at baseline. There were also no significant
differences in indexes derived from CGM between the groups at baseline.

CGM showed that 24-hour mean glucose and postprandial glucose after each
meal decreased significantly after treatment with tofogliflozin in
patients receiving or not receiving DPP-4 inhibitors (Fig. 1A and B, and
Table 2). Time in range increased significantly after treatment in both
the group receiving DPP-4 inhibitors (from 54.9\% \selectlanguage{ngerman}± 27.8\% to 78.2\% ±
22.2\%, respectively; \emph{P} = 0.0120) and the group not receiving
them (from 65.5\% ± 33.9\% to 83.9\% ± 20.2\%, respectively; \emph{P} =
0.0276), and time above range significantly decreased in both groups
(Table 2).

After treatment with tofogliflozin, the SD of 24-hour glucose
significantly decreased in the group receiving DPP-4 inhibitors (from
40.80 ± 17.89 mg/dL to 29.70 ± 10.23 mg/dL, \emph{P} = 0.0108; Table 2)
but did not significantly change in the group not receiving DPP-4
inhibitors (P=0.1028). In patients receiving DPP-4 inhibitors, MAGE was
significantly reduced (from 98.8 ± 41.6 mg/dL to 70.9 ± 29.3 mg/dL,
\emph{P} = 0.0066), as was MPPGE (from 77.2 ± 41.8 mg/dL to 63.8 ±3 2.1
mg/dL, P = 0.0378); however, both these indexes of glycemic variability
were unchanged in patients not receiving DPP-4 inhibitors (Table 2).

\textbf{Discussion}

In the present study, we found that tofogliflozin acutely decreased
24-hour mean glucose levels and postprandial glucose levels after each
meal and increased time in range in patients with type 2 diabetes,
irrespective of treatment with DPP-4 inhibitors. These findings are in
agreement with previous studies, including ours (5, 9-11). In a previous
study with CGM, we also demonstrated that acute dosing with a single
tablet of canagliflozin, another SGLT2 inhibitor, caused a significant
reduction in 24-hour mean glucose levels (10). Another study also found
that an SGLT2 inhibitor lowered glucose levels from 2 hours after a
single dose and improved glycemic variability within 1 week of treatment
(11). The finding that tofogliflozin significantly reduced postprandial
glucose after each meal is in accordance with other CGM studies on the
SGLT2 inhibitor class (5, 9-12). In the present study, we could confirm
by CGM that tofogliflozin rapidly lowers blood glucose levels.

This is the first study to compare the acute effects of a SGLT2
inhibitor on the 24-hour glucose profile and glycemic variability
evaluated by CGM between patients receiving and those not receiving
DPP-4 inhibitors. CGM revealed that the SD of 24-hour glucose levels, an
index of glycemic variability, was significantly reduced in patients
receiving DPP-4 inhibitors but was unchanged in those not receiving
these drugs. Moreover, both MAGE and MPPGE, other indexes of glycemic
variability, were significantly reduced only in patients receiving DPP-4
inhibitors. Thus, SGLT2 inhibitors may improve glycemic variability more
strongly as an add-on treatment in patients receiving DPP-4 inhibitors
than in patients not receiving DPP-4 inhibitors. Several studies
reported that glucose fluctuations have a more specific triggering
effect on oxidative stress than chronic sustained hyperglycemia (13-14).
We speculate that improvement of glycemic variability by tofogliflozin
may suppress development of cardiovascular events in patients with type
2 diabetes, especially those receiving DPP-4 inhibitors.

The mechanisms by which add-on therapy with tofogliflozin reduces
glycemic variability only in patents receiving DPP-4 inhibitors remains
unclear. One possible explanation is that DPP-4 inhibitors, which
inhibit glucagon secretion and promote insulin secretion by enhancing
the effects of the incretin hormone GLP-1, may potentially attenuate the
increase in hepatic glucose production induced by SGLT2 inhibitors (5,
6). In a previous study, we demonstrated that, during a meal test,
plasma glucagon level was significantly reduced 30 minutes after
treatment with teneligliptin (a DPP-4 inhibitor) compared with baseline
(15). Enhancement of GLP-1 action by DPP-4 inhibitors may increase
insulin secretion and suppress glucagon release in a glucose-dependent
manner, leading to a decrease in postprandial glucose levels. Adding
SGLT2 inhibitors to existing DPP-4 inhibitors could suppress EGP
secondary to excess excretion of glucose into urine because treatment
with DPP-4 inhibitors can offset SGLT2-induced EGP by inhibiting
glucagon secretion and simulating insulin secretion. A previous study
with CGM demonstrated that add-on therapy with canagliflozin did not
increase fasting or postprandial plasma glucagon in patients with type 2
diabetes receiving teneligliptin (16). Taken together, the findings
indicate that a combination of SGLT2 inhibitors and DPP\selectlanguage{english}-4 inhibitors may
be an effective treatment for patients with type 2 diabetes because of
the complementary pharmacological effects of these drugs, ie, because of
the opposite mechanisms of action of DPP-4 inhibitors and SGLT2
inhibitors on EGP, and because both medications have a fairly low risk
of hypoglycemia (17).

The present study clearly has some limitations. First, the number of
participants was small, so the results need to be confirmed in a larger
study. Second, we did not measure plasma glucagon or insulin levels
during CGM, so we could not prove that DPP-4 inhibitors counteract
SGLT2-induced EGP by inhibiting glucagon secretion and simulating
insulin secretion.

In conclusion, add-on therapy of tofogliflozin to DPP-4 inhibitors
acutely reduces 24-hour mean glucose levels and improves glycemic
variability in patients with type 2 diabetes.



\textbf{Declaration of conflicting interests}

The author(s) declared no potential conflicts of interest with respect
to the research, authorship and/or publication of this article.

\textbf{Funding}

The author(s) received no financial support for the research, authorship
and/or publication of this article.

\textbf{Author contributions:} TI, SH, HK, HK, and SS contributed to the
study design, data collection, and drafting of the manuscript; TT, TJ,
and IU contributed to the discussion and reviewed the manuscript; IU
reviewed and edited the manuscript; and TI and YA researched the data
and wrote, reviewed, and edited the manuscript.



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\textbf{Figure legends}

Fig.1

The average glucose levels before and after treatment with tofogliflozin
20 mg/day in patients with type 2 diabetes receiving (A) or not
receiving dipeptidyl peptidase-4 (DPP-4) inhibitors (B).

\textbf{Hosted file}

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\textbf{Hosted file}

\verb`Table 2  Changes in CGM parameters after treatment with tofogliflozin.doc`  available at \url{https://authorea.com/users/308349/articles/524548-acute-effect-of-add-on-therapy-with-tofogliflozin-a-sodium-glucose-co-transporter-2-inhibitor-on-24-hour-glucose-profile-and-glycemic-variability-evaluated-by-continuous-glucose-monitoring-in-patients-with-type-2-diabetes-receiving-dipeptidyl-peptidase-4-inhibitors}

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