T2DM	Type 2 diabetes
GLP-1RA	Glucagon like peptide-1 receptor agonists
PPAR	Peroxisome proliferator-activated receptor
IR	Insulin receptor
IRS	Insulin receptor substrate
PI3K	Phosphatidylinositol 3-kinase
Akt	Serine/threonine kinase
MAPK	Mitogen-activated protein kinase
ERK	Extracellular signal-regulated kinase
GLP-1	Glucagon-like peptide-1
MDD	Major depressive disorder
GDS	Geriatric Depression Scale
HADS	Hospital Anxiety and Depression Scale
HPA	Hypothalamic–Pituitary–Adrenal
TSST	Trier Social Stress Test
MADRS	Montgomery Åsberg Depression Rating Scale
PANAS	Positive and Negative Affect Schedule
BDI	Beck Depression Inventory
RCT	Randomized clinical trial
HDRS	Hamilton Depression Rating Scale
PCOS	Polycystic ovarian syndrome
MetS	Metabolic syndrome
IDS	Inventory of Depressive Symptomatology
HOMA-IR	Homeostatic model assessment of insulin resistance
QIDS	Quick Inventory of Depressive Symptoms
OR	Odds ratio
CI	Confidence interval
NIRKO	Neuronal-specific knockout of insulin receptor
BCAA	Branched chain amino acids
LAT	Large neutral amino acid transporter
IO and NS	Immune/Inflammatory and Oxidative, and Nitrosative Stress
IL	Interleukin
TNF	Tumor necrosis factor
CRP	C-reactive protein
CNS	central nervous system
IDO	Indolemaine 2,3-dioxygenase
SERT	serotonin transporter
IKKβ	IκB kinase β
NKκB	nuclear factor κB
JNK	c-Jun N-terminal kinase
BBB	Blood–Brain barrier
HDL-c	High-density lipoprotein cholesterol
MDA	Malondialdehyde
CAT	Catalase
SOD	Superoxide dismutase
GSH	Glutathione
PON1	Paraoxonase 1
ROS	Reactive oxygen species
NO	Nitric oxide
NOS	Nitric oxide synthase
SAPK	Stress-activated kinases
LTP	Long-term potentiation
LTD	Long-term depression
NMDA	N-methyl-d-aspartate
AMPA	a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid
IGF	Insulin-like growth factor
BDNF	Brain-derived neurotrophic factor
FOXO	Forkhead box O transcription factor
GC	Glucocorticoid
CRH	Corticotropin releasing hormone
cAMP	Cyclic adenosine monophosphate
PKA	Protein kinase A
STAT	Signal transducer and activator of transcription
GSK	Glycogen synthase kinase
Nrf2	Nuclear factor erythroid 2-related factor 2
COMT	Catechol O-methyltransferase